Developer carrier, developing device using the developer carrier, and process cartridge using the developer carrier

ABSTRACT

A developer carrier is provided which is capable of stably imparting charging to a toner over a long term without change of a physical shape of its surface, material composition, and the like even in endurable use and which is capable of forming a satisfactory image while avoiding the occurrence of toner contamination and toner charge-up. That is, the developer carrier is characterized in that: it comprises at least a substrate and a resin coating layer formed on a surface of the substrate; and the resin coating layer comprises at least graphitized particles (i) with a degree of graphitization p(002) of 0.20 to 0.95 and an indentation hardness HUT [68] of 15 to 60 or graphitized particles (ii) with a degree of graphitization p(002) of 0.20 to 0.95 and an average circularity SF-1 of 0.64 or more.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a developer carrier used in adeveloping device for developing and visualizing a latent image formedon an image-bearing member such as an electrophotographic photosensitivemember or an electrostatic recording derivative. Further, the presentinvention relates to a developing device and a process cartridge each ofwhich uses the developer carrier.

[0003] 2. Description of the Related Art

[0004] Up to now, various electrophotographic methods have been known.Generally with the methods, an electrical latent image is formed on anelectrostatic latent image holding member (photosensitive drum) with theuse of various means by using a photoconductive material; then, theelectrostatic latent image is subjected to developing with a developer(toner) to be visualized; a toner image is transferred onto atransferring material such as paper as the occasion demands; andthereafter, the toner image is fixed onto the transferring material withheat, pressure etc., thereby obtaining a copied material.

[0005] Developing systems in the electrophotographic methods are mainlydivided into one-component developing systems and two-componentdeveloping systems. In recent years, a copying device part needs to bereduced in size with the purpose of attaining reduction in weight and insize of an electrophotographic device. Thus, a developing device thatuses the one-component developing system is used in many cases.

[0006] The one-component developing system does not require carrierparticles such as glass beads or iron powder differently from thetwo-component developing system, and thus, reduction in size and inweight of the developing device itself can be attained. On the otherhand, in the two-component developing system, a toner density in adeveloper needs to be maintained at a constant level, and thus, a devicefor detecting a toner density and supplying a necessary amount of toneris required. Therefore, a large and heavy developing device is providedhere. The one-component developing system does not require such adevice, and thus, is preferable in the point that a developing devicecan be reduced in size and in weight.

[0007] As the developing device using the one-component developingsystem, the following one is known. With the device, first, anelectrostatic latent image is formed on a surface of a photosensitivedrum serving as an electrostatic latent image holding member; a positiveor negative charge is imparted to a toner through friction between adeveloper carrier (developing sleeve) and the toner and/or a developerlayer thickness regulating member for regulating a toner coating amounton the developing sleeve and the toner; then, the toner imparted withthe charge is thinly applied on the developing sleeve, and is fed to adeveloping region where the photosensitive drum and the developingsleeve face to each other; the toner is flied and adhered to theelectrostatic latent image on the surface of the photosensitive drum inthe developing region, whereby the electrostatic latent image isvisualized as a toner image.

[0008] However, in the case of using the above-mentioned one-componentdeveloping system, charging property of the toner is difficult to beadjusted. Although various devices on the toner are implemented, theproblems on nonuniformity of toner charging and endurance stability ofcharging have not been completely solved.

[0009] In particular, there tends to occur, specially under lowhumidity, a so-called charge-up phenomenon: in which a charging amountof the toner coated onto the developing sleeve is excessively increaseddue to the contact with the developing sleeve while the developingsleeve rotates repeatedly; then, the toner and the surface of thedeveloping sleeve attract each other due to a reflection forcetherebetween so that the toner is fixed on the developing sleevesurface; and the toner does not move to a latent image on thephotosensitive drum from the developing sleeve. When the above-mentionedcharge-up phenomenon occurs, the toner as an upper layer is difficult tobe charged, and a developing amount of the toner is reduced. Thus, theproblems of thinning of a line image, reduction in image density of asolid image, and the like arise. Further, there occurs a so-calledblotch phenomenon in which: the toner, which is not properly charged dueto charge-up, is failingly regulated and flows onto the sleeve; and thetoner is formed into spotted or wave-shape unevenness.

[0010] Further, the respective formation states of a toner layer arechanged in an image portion (toner consumption portion) and a non-imageportion, so that the charging states differs therebetween. Therefore,there tends to occur a so-called sleeve ghost phenomenon in which, forexample, when the position where a solid image with a high image densityhas been developed once on the developing sleeve corresponds to thedevelopment position in the next rotation time of the developing sleeveand a half-tone image is developed at the developing position, a mark ofthe solid image appears on the image.

[0011] Moreover, reduction in particle diameter and reduction towardfiner particle of the toner are promoted for the purpose of realizingdigitization of electrophotographic devices and higher image quality.For example, in order to improve resolution and character sharpness andfaithfully reproduce the latent image, there is generally used a tonerwith a weight average particle diameter of about 5 to 12 μm. Further,from the viewpoint of ecology, with the goal of attaining the furtherreduction in weight, size, etc. of the device, the following improvementof transfer efficiency of the toner is promoted in order to decrease awaste toner. For example, a transfer efficiency enhancer with an averageparticle diameter of 0.1 to 3 μm and hydrophobic silica impalpablepowder with a BET specific surface area of 50 to 300 m²/g are made to becontained in a toner, whereby the volume resistance of the toner isreduced, and a thin film layer of the transfer efficiency enhancer isformed on the photosensitive drum. As a result, the transfer efficiencyis enhanced. Further, the toner itself is processed to have a sphericalshape with a mechanical impact force, and thus, the transfer efficiencyis improved.

[0012] Furthermore, there is a tendency that a toner fixationtemperature is lowered with the purpose of attaining the reduction of afirst copy time and the saving electricity. Under such circumstances, inparticular, the toner under low temperature and low humidity is easy toelectrostatically adhere onto the developing sleeve because the chargeamount per unit mass of the toner increases; on the other hand, thetoner under high temperature and high humidity is easy to be changed inquality due to a physical force from the outside or because of the factthat the toner is made of a material apt to be fluidized. Therefore,sleeve contamination and sleeve fusion are easy to develop.

[0013] As a method of solving the above-mentioned phenomena, there isproposed, in JP 02-105181 A, JP 03-036570 A, and the like, a method thatuses a developing sleeve that is formed by providing a coating layer,which is made by dispersing conductive impalpable powder such ascrystalline graphite and carbon in resin, on a metal substrate. It isrecognized that the above-mentioned phenomena are significantly reducedby using the method.

[0014] However, in the case of the addition of a large amount of thepowder, the method is effective in avoiding the occurrence of charge-upand sleeve ghost. However, moderate charging imparting ability to thetoner is insufficient, and a sufficient image density is difficult to beobtained particularly in a high-temperature and high-humidityenvironment. Further, in the case of the addition of the large amount ofthe powder, the coating layer becomes brittle and easy to be scrapedoff, and also, the shape of the layer surface becomes nonuniform. Thus,in the case where the endurable use proceeds, surface roughness andsurface composition of the coating layer are changed, and feedingfailure of the toner and nonuniformity of charge impartation to thetoner occur easily.

[0015] In the case of using the coating layer in which the crystallinegraphite is dispersed, the surface of the coating layer has lubricitythat arises from the scaly structure of the crystalline graphite. Thus,the coating layer sufficiently exhibits an effect on the prevention ofthe occurrence of charge-up and sleeve ghost, but the scaly shape makesthe surface shape of the coating layer nonuniform. Further, since thehardness of the crystalline graphite is low, wear and desorption of thecrystalline graphite itself are easy to occur on the coating layersurface. In the case where the endurable use proceeds, surface roughnessand surface composition of the coating layer are changed, which mayeasily lead to feeding failure of the toner and nonuniformity of chargeimpartation to the toner.

[0016] On the other hand, in the case where the addition amount of theconductive impalpable powder in the coating layer formed on the metalsubstrate of the developing sleeve is small, the effect of theconductive impalpable powder such as crystalline graphite and carbon islimited. Thus, such a problem is left in that the measures againstcharge-up and sleeve ghost are insufficient.

[0017] Further, in JP 03-200986 A, there is proposed a developing sleevein which a conductive coating layer, in which conductive impalpablepowder such as crystalline graphite and carbon, and further sphericalparticles are dispersed in resin, is provided on a metal substrate. Withthe developing sleeve, wear-resistance of the coating layer is enhancedto some extent, the shape of the coating layer surface is made uniform,and change in surface roughness due to endurable use is relativelysmall. Therefore, toner coating on the sleeve is stabilized, and tonercharging can be made uniform up to a point. As a result, there arises noproblem on sleeve ghost, image density, image density unevenness, andthe like, and there is a tendency of image quality to be stabilized.However, even the developing sleeve is insufficient for stabilization ofmoderate charging imparting ability to a toner, and quick and uniformcharging controllability to a toner. Further, in terms ofwear-resistance as well, the change in roughness and nonuniformity inroughness of the coating layer surface, which arise from wear ordesorption of the spherical particles and crystalline graphite containedin the coating layer in the developing sleeve, and the following tonercontamination, toner fusion, and the like on the coating layer occur dueto the further endurable use over a long term. In this case, tonercharging becomes unstable, which becomes the cause of image defect.

[0018] Further, proposed in JP 08-240981 A is a developing sleeve inwhich: conductive spherical particles with low specific gravity areuniformly dispersed in a conductive coating layers thereby enhancingwear-resistance of the coating layer and making the shape of the coatinglayer surface uniform, which increases uniform charging impartingproperty to a toner; and toner contamination and toner fusion aresuppressed even when the coating layer is somewhat worn. However, eventhe developing sleeve is incomplete in point of quick and uniformcharging imparting property to a toner and moderate charging impartingability to a toner. Moreover, as to the wear-resistance as well, theconductive particles such as the crystalline graphite are apt to wearand fall off from the portion where the conductive spherical particlesdo not exist on the coating layer surface in the further endurable useover a long term. The wear of the coating layer is promoted from theportion where the particles wear and fall off, whereby tonercontamination and toner fusion are caused. As a result, toner chargingbecomes unstable, which becomes the cause of image defect.

SUMMARY OF THE INVENTION

[0019] The present invention has been made in view of the aboveproblems. That is, the object of the present invention is to provide adeveloper carrier with which a high-quality image, which is uniform, isfree from density unevenness, and has high image density, can beobtained without the problems of density lowering, image densityunevenness, sleeve ghost, fog, and the like under differentenvironmental conditions and to provide a developing device and aprocess cartridge each of which uses the developer carrier.

[0020] Another object of the present invention is to provide adeveloping carrier which can reduce toner adhesion to a surface thereofwhen a toner having a small particle diameter or a spherical toner, sothat the developing carrier can charge a toner properly and immediatelyand prevent the toner from being ununiformly charged, and to provide adeveloping device and a process cartridge each of which uses thedeveloper carrier.

[0021] Also, another object of the present invention is to provide adeveloper carrier with which: deterioration of a resin coating layer ona surface of the developer carrier, which arises from repeated copyingor endurable use, is hardly occured; high durability is provided; andstable image quality is obtained and to provide a developing device anda process cartridge each of which uses the developer carrier.

[0022] Further, another object of the present invention is to provide adeveloper carrier which: can quickly and uniformly charge a tonerthereon; and can charge the toner stably without causing charge-up evenin repeated copying over a long term, to thereby obtain a high-qualityimage having uniform density and is free from image density lowering,density unevenness, and fog and to provide a developing device and aprocess cartridge each of which uses the developer carrier.

[0023] The present invention relates to a developer carrier that carriesa developer for visualizing an electrostatic latent image retained on anelectrostatic latent image-bearing member, in which:

[0024] the developer carrier comprises at least a substrate and a resincoating layer formed on a surface of the substrate;

[0025] the resin coating layer comprises at least graphitized particles(i) with a degree of graphitization p(002) of 0.20 to 0.95 and anindentation hardness HUT [68] of 15 to 60 or graphitized particles (ii)with a degree of graphitization p(002) of 0.20 to 0.95 and an averagecircularity SF-1, which is an average value of circularity obtained bythe following expression (1), of 0.64 or more.

Circularity=(4×A)/{(ML)²×π}  (1)

[0026] [In the expression, ML represents the maximum length ofPythagorean theorem of a particle projected image, and A represents anarea of the particle projected image.]

[0027] The present invention further relates to a developing device anda process cartridge using the developer carrier.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the accompanying drawings:

[0029]FIG. 1 is a sectional schematic diagram showing a part of adeveloper carrier according to the present invention;

[0030]FIG. 2 is a sectional schematic diagram showing a part of thedeveloper carrier according to the present invention;

[0031]FIG. 3 is a sectional schematic diagram showing a part of thedeveloper carrier according to the present invention;

[0032]FIG. 4 is a sectional schematic diagram showing a part of thedeveloper carrier according to the present invention;

[0033]FIG. 5 is a schematic diagram of an embodiment of a developingdevice according to the present invention in the case of using amagnetic one-component developer;

[0034]FIG. 6 is a schematic diagram of another embodiment of adeveloping device according to the present invention;

[0035]FIG. 7 is a schematic diagram of another embodiment of thedeveloping device according to the present invention;

[0036]FIG. 8 is a schematic diagram of an embodiment of the developingdevice according to the present invention in the case of using anon-magnetic one-component developer;

[0037]FIG. 9 is a schematic structural diagram of an example of an imageforming apparatus according to the present invention;

[0038]FIG. 10 is a schematic structural diagram of an example of aprocess cartridge according to the present invention;

[0039]FIG. 11 is a schematic structural diagram of another example ofthe image forming apparatus according to the present invention;

[0040]FIG. 12 is a sectional schematic diagram showing a part of adeveloper carrier according to the present invention;

[0041]FIG. 13 is a sectional schematic diagram showing a part of adeveloper carrier according to the present invention;

[0042]FIG. 14 is a sectional schematic diagram showing a part of adeveloper carrier according to the present invention;

[0043]FIG. 15 is a sectional schematic diagram showing a part of adeveloper carrier according to the present invention;

[0044]FIG. 16 is a schematic diagram of a specific example of a devicesystem for manufacturing a toner; and

[0045]FIG. 17 is a schematic sectional diagram of an example of amechanical pulverizer used in a toner pulverizing step.

DETAILED DESCRIPTION OF THE INVENTION

[0046] Hereinafter, the present invention will be described in detailwith preferred embodiments given. First, description is made of adeveloper carrier according to the present invention.

[0047] First of all, Embodiment 1 of the present invention will bedescribed.

[0048] The developer carrier according to the present invention carriesa developer for visualizing an electrostatic latent image retained on anelectrostatic latent image-bearing member, and comprises at least asubstrate and a resin coating layer formed on a surface of thesubstrate. The developer carrier of the present invention ischaracterized in that the resin coating layer contains at leastgraphitized particles (i) with a degree of graphitization p(002) of 0.20to 0.95 and an indentation hardness HUT[68] of 15 to 60 or graphitizedparticles (ii) with a degree of graphitization p(002) of 0.20 to 0.95and an average circularity SF-1, which is an average value ofcircularity obtained by the following expression (1), of 0.64 or more.

Circularity=(4×A)/{(ML)²×π}  (1)

[0049] [In the expression, ML represents the maximum length ofPythagorean theorem of a particle projected image, and A represents anarea of the particle projected image.]

[0050] The resin coating layer comprising the graphitized particles (i)with a degree of graphitization p(002) of 0.20 to 0.95 and anindentation hardness HUT[68] of 15 to 60 or the graphitized particles(ii) with a degree of graphitization p(002) of 0.20 to 0.95 and anaverage circularity SF-1, which is an average value of circularity andis obtained by the above expression (1), of 0.64 or more can form theuniform surface roughness to the resin coating layer, and at the sametime, even in the case where the coating layer surface is worn, thesurface roughness changes little. Further, since the above-mentionedresin coating layer is excellent in lubricity and uniform conductivity,the developer carrier hardly contaminated by a developer and thedeveloper hardly weld to the developer carrier. Further, when beingcontained in the resin coating layer that constitutes the developercarrier, the graphitized particles (i) and (ii) have an effect inenhancing the property of immediately and uniformly charging the tonercontained in the developer.

[0051] The degree of graphitization p(002) indicates a p value ofFranklin, which is obtained by measuring a lattice spacing d(002)obtained from an X-ray diffraction pattern of graphite with thefollowing expression.

d(002)=3.440−0.086(1−p(002 )²)

[0052] The p(002) value indicates the ratio of a disordered part of alamination of carbon hexagonal planes, and the smaller the p(002) valueis, the higher the crystallization becomes.

[0053] JP 02-105181 A, JP 03-36570 A, and the like disclose of adeveloper carrier comprising coating layer on surface thereof. Thecrystalline graphite-such as artificial graphite; which is obtained byhardening and molding an aggregate such as coke with tar pitch; burningit at approximately 1000 to 1300° C., and graphitizing it atapproximately 2500 to 3000° C.; or natural graphite is used in thecoating layer. The graphitized particles used in the present inventiondiffer from the above crystalline graphite in raw material andmanufacturing steps. The graphitized particles used in the presentinvention have a degree of graphitization little lower than thecrystalline graphite as disclosed in the above publication, but havehigh conductivity and lubricity similarly to the crystalline graphite.Further, the graphitized particles used in the present invention havecharacteristics that they each have a substantially spherical shape anda relatively high hardness, differently from the crystalline graphitehaving a scaly or acicular shape. Therefore, since the graphitizedparticles having the above-mentioned characteristics can be uniformlydispersed in a resin coating layer, and therefore a surface of the resincoating layer is made to have uniform surface roughness and highabrasion resistance. In addition, the shape of the graphitized particleitself hardly changes. Thus, even if scraping of the coating resin etc.in the resin coating layer is scraped, and this causes the particleitself to fall off, the particle may be projected and exposed again fromthe resin layer. Thus, the change in surface shape of the resin coatinglayer can be lowered.

[0054] Further, when the graphitized particles are contained in theresin coating layer on the surface of the developer carrier, moreenhancement of immediate and uniform frictional charging ability to thetoner can be realized, compared with the case of using the conventionalcrystalline graphite, without causing charge-up of the toner on theresin coating layer surface.

[0055] The degree of graphitization p(002) of the graphitized particlesused in the present invention is 0.20 to 0.95. The p(002) is preferably0.25 to 0.75, and is more preferably 0.25 to 0.70.

[0056] In the case of the p(002) exceeding 0.95, abrasion resistance ofthe resin coating layer is excellent, but the charge-up of the toner mayoccur along with the reduction of conductivity or lubricity of thedeveloper carrier, which may lead to degradation of sleeve ghost, fog,and image quality such as image density. Further, in the case of usingan elastic blade in a developing step, the blade may be scratched, as aresult of which streaks, density unevenness, and the like may be easilyproduced in an image. On the other hand, in the case of the p(002) ofless than 0.20, degradation of the abrasion resistance of thegraphitized particles causes the reduction of the abrasion resistance ofthe resin coating layer surface and the reduction of the mechanicalstrength and immediate and uniform charging property to the tonercarried on the resin coating layer.

[0057] Moreover, the graphitized particles used in the present inventionare characterized by having an indentation hardness HUT[68] of 15 to 60.The indentation hardness HUT[68] is preferably 20 to 55, and is morepreferably 25 to 50.

[0058] In the case of the indentation hardness HUT[68] of less than 15,the abrasion resistance, mechanical strength, and immediate and uniformcharging property to the toner of the resin coating layer tend to belowered. On the other hand, in the case of the indentation hardnessHUT[68] exceeding 60, the abrasion resistance of the resin coating layeris excellent, but the charge-up of the toner may occur along with thereduction of conductivity or lubricity of the developer carrier, whichmay lead to degradation of sleeve ghost, fog, and image quality such asimage density.

[0059] The indentation hardness HUT[68] in the present inventionindicates the indentation hardness HUT[68] measured by using MicroHardness Tester MZT-4 manufactured by Akashi Corp. with atriangular-pyramid diamond indenter with a face angle of 68 degrees withrespect to an axial core, and is expressed by the following expression(2):

Indentation hardness HUT[68]=K×F/(h2)²   (2)

[0060] [where K: coefficient, F: test load, h2: maximum indentationdepth of the indenter].

[0061] The hardness can be measured with a small load compared withmeasurement of other hardness. As to the material having elasticity orplasticity as well, the hardness including elastic deformation orplastic deformation can be obtained. Thus, the indentation hardness ispreferably used. Note that a specific measurement method of theindentation hardness (HUT[68]) in the present invention will bedescribed below.

[0062] Further, as to the graphitized particles used in the presentinvention, it is preferable that an average circularity SF-1 thereof,which is an average value of circularity and is obtained with the aboveexpression (1), is 0.64 or more, more preferably 0.66 or more, and stillmore preferably 0.68 or more.

[0063] In the case of the average circularity SF-1 of less than 0.64,dispersion property of the graphitized particles in the resin coatinglayer lowers, and the surface roughness of the resin coating layer maybecome ununiform, which is not preferable in terms of the immediate anduniform charge of the toner, the abrasion resistance and strength of theresin coating layer.

[0064] In the present invention, the average circularity SF-1 of thegraphitized particles indicates the average value of the circularityobtained by the above expression (1).

[0065] In the present invention, in the specific method of measuring theaverage circularity SF-1, a projected image of the graphitizedparticles, which is magnified by an optical system, is captured into animage analyzer; values of circularity of the respective particles arecalculated; and the values are averaged, thereby obtaining the averagecircularity SF-1.

[0066] In the present invention, the measurement of the circularity isperformed in a limited particle range from a equivalent circle diameterof 2 μm or more, from which the average value is obtained withreliability and which greatly influences the characteristics of theresin coating layer. Further, the measurement is performed with thenumber of measurement particles of about 3000 or more, preferably 5000or more in order to obtain the value with reliability. Note that aspecific measurement method of the average circularity SF-1 in thepresent invention will be described below.

[0067] The graphitized particles used in the present inventionpreferably have a number-average particle diameter of 0.5 to 25 μm, morepreferably 1 to 20 μm.

[0068] In the case where the number-average particle diameter of thegraphitized particles is less than 0.5 μm, the effect of impartinguniform roughness and lubricity to the surface of the resin coatinglayer and the effect of enhancing charging ability to the toner arelittle, immediate and uniform charging of the toner is insufficient.Further, the toner charge-up, contamination of the developer carrier bythe toner, and toner weld to the developer carrier are generated. As aresult, degradation of ghost and lowering of image density may beoccurred and therefore, it is not preferable. Further, in the case ofthe number-average particle diameter exceeding 25 μm, the roughness ofthe coating layer surface becomes too large, charging to the toner isdifficult to be sufficiently performed, and also, the mechanicalstrength of the coating layer is reduced. Therefore, this is notpreferable.

[0069] The number-average particle diameter of the graphitized particlesdiffers depending on raw materials and manufacturing methods to be used.However, the number-average particle diameter can be adjusted bycontrolling a particle diameter of a raw material before graphitizationthrough pulverization or classification or by performing furtherclassification of the graphitized particle after graphitization.

[0070] The following methods are preferable as methods for obtaining thegraphitized particles (i) with the above-mentioned degree ofgraphitization p(002) and indentation hardness HUT[68] and/or thegraphitized particles (ii) with the above-mentioned degree ofgraphitization p(002) and average circularity SF-1. However, the presentinvention is not limited to the following methods.

[0071] A method of obtaining particularly preferable graphitizedparticles to be used in the present invention is a method ofgraphitizing single-phase particles having optical anisotropy such asmeso-carbon micro beads or bulk mesophase pitch as a raw material. Sucha method is preferable to increase the degree of graphitization of thegraphitized particles to keep the lubricity thereof while retaining theappropriate hardness and generally spherical shape of the graphitizedparticles.

[0072] The optical anisotropy of the above raw material is caused by thelamination of aromatic molecules and a orderliness of the raw materialis further promoted by the graphitization process, resulting ingraphitized particles having a higher degree of graphitization.

[0073] When the bulk mesophase pitch described above is used as a rawmaterial for obtaining graphitized particles to be used in the presentinvention, it is preferable to use one to be softened and melted underheating for obtaining spherical graphitized particles having a higherdegree of graphitization.

[0074] A typical method of obtaining the above bulk mesophase pitch is,for example, a method in which β-resin is extracted from coal-tar pitchor the like with solvent fractionation and the extracted β-resin ishydrogenated and is changed to be heavy-duty to obtain bulk meso-phasepitch. In the above method, the extracted β-resin may be pulverizedafter changed to be heavy-duty and then a solvent soluble fraction isremoved by benzene, toluene, or the like to obtain bulk mesophase pitch.

[0075] The bulk mesophase pitch preferably contains less than 95% byweight of a quinoline soluble fraction. If it is less than 95% byweight, a liquid-phase carbonization in the inside of particles becomesdifficult to occur and the particles that are solid-phase carbonized areremained in a crushed shape. Therefore, the spherical powders are hardlyobtained.

[0076] The bulk mesophase pitch obtained as described above can begraphitized by the following method. At first, the above bulk mesophasepitch is pulverized into 2 to 25 μm in size and is then subjected toheat treatment at 200 to 350° C. in the air for oxidizing the pitchslightly. Such an oxidation treatment only makes the surface of the bulkmesophase pitch infusible to prevent the pitch from being melted andfused in the subsequent steps of graphitization baking. This oxidizedbulk mesophase pitch may preferably contain 5 to 15% by weight ofoxygen. If the content of oxygen is less than 5% by weight, it is notpreferable because the particles are vigorously fused together when heattreatment is performed. If it is more than 15% by weight, the oxidationproceeds up to the inside of the particle so that spherical products arehardly obtained as the particles should be graphitized while keeping acrushed shape of the particle.

[0077] Subsequently, the oxidized bulk mesophase pitch is subjected toprimary baking at about 800 to 1,200° C. under the atmosphere of inertgas such as nitrogen or argon to carbonize the pitch, followed by beingsubjected to secondary baking at about 2,000 to 3,500° C. to obtaindesired graphitized particles.

[0078] As a method of obtaining meso-carbon micro beads which areanother preferable raw material for obtaining the graphitized particlesto be used in the present invention, a typical example thereof will bedescribed below. At first, coal heavy oil or petroleum heavy oil ispoly-condensed by heating at 300 to 500° C. to generate crude mesocarbonmicro beads. The resulting product is further subjected to filtration,standing sedimentation, centrifugal separation, and so on to isolatemesocarbon micro beads, followed by washing with a solvent such asbenzene, toluene or xylene and drying.

[0079] Upon the graphitization, for preventing the graphitized particlesfrom coagulating while obtaining uniform particle size, after abovedrying, it is preferable to subject the resulting mesocarbon micro beadsto primary dispersion with a moderate mechanical force as to prevent themesocarbon micro beads from breaking.

[0080] The meso-carbon micro beads after the primary dispersion arecarbonized by primary baking at 200 to 1,500° C. under inert atmosphere.For preventing the graphitized particles from coagulating whileobtaining uniform particle size, the carbonized product after theprimary baking is also preferable to be subjected to dispersion with amoderate mechanical force as to prevent the carbonized product frombreaking. The carbonized product after the primary baking is subjectedto secondary baking at a temperature of about 2,000 to 3,500° C. underinert atmosphere to obtain desired graphitized particles.

[0081] Furthermore, in all the cases of using any one of thesemanufacturing processes, graphitized particles obtained from any one ofthe above raw materials may preferably have uniform particle sizedistribution to a certain extent through classification for attaining auniform surface form of the resin coating layer.

[0082] In any one of the methods for producing graphitized particlesusing any one of the raw materials, the temperature of baking forgraphitization is preferably in the range of 2,000 to 3,500° C., morepreferably in the range of 2,300 to 3,200° C.

[0083] When the graphitization is performed with baking at a temperatureof 2,000° C. or less, the degree of graphitization of graphitizedparticles may be insufficient, so that the charge-up of toner may occuras a result of lowering conductivity or lubricity. Therefore, thequality of an image tends to be deteriorated regarding sleeve ghost orfogging, or a decrease in image density. Furthermore, when an elasticblade is used, the blade scratches may be caused and thus troubles suchas streak and uneven image density tend to occur on an image.Furthermore, when the baking temperature is 3,500° C. or higher, thedegree of graphitization of graphitized particles may increase too much.Therefore, the hardness of graphitized particles may decrease todeteriorate the abrasion resistance thereof. As a result, there is atendency of decreasing the abrasion resistance of the resin coatinglayer surface, and the mechanical strength and toner-charging propertyof the resin coating layer.

[0084] In the present invention, the coefficient of friction Ps of theresin coating layer of the developer carrier may preferably meet0.10≦μs≦0.35, more preferably 0.12≦μs≦0.30. When the coefficient offriction μs of the resin coating layer is less than 0.1, thedeveloper-transporting property decreases. In some cases, therefore, asufficient image density may be hardly obtained. On the other hand, whenthe coefficient of friction μs of the resin coating layer is more than0.35, the charge up of toner tends to occur. Therefore, the surface ofthe resin coating layer may be stained or fused with toner, so that theimage quality tends to be deteriorated as to sleeve ghost, fogging,uneven image density, and so on.

[0085] The above ranges of the coefficient of friction μs of the resincoating layer can be attained by dispersing the graphitized particlesused in the present invention into the coating resin layer.

[0086] A coating resin material for the resin coating layer thatconstitutes the developer carrier of the present invention may be anyone of well-known resins generally used in the resin coating layer ofthe conventional developer carrier. For example, the coating resinmaterial may be formed of: a thermoplastic resin such as styrene resin,vinyl resin, polyether sulfone resin, polycarbonate resin, polyphenyleneoxide resin, polyamide resin, fluorine resin, cellulose resin, or acrylresin; or a heat- or photo-curable resin such as epoxy resin, polyesterresin, alkyd resin, phenol resin, melamine resin, polyurethane resin,urea resin, silicon resin, or polyimide resin. Among them, a resinhaving mold-releasing characteristics such as silicon resin or fluorineresin is more preferable. Alternatively, a resin having excellentmechanical characteristics such as polyether sulfone resin,polycarbonate resin, polyphenylene oxide resin, polyamide resin, phenolresin, polyester resin, polyurethane resin, styrene resin, or acrylresin is more preferable.

[0087] In the present invention, the volume resistivity of the resincoating layer of the developer carrier is preferably in the range of10⁻² to 10⁵ Ω·cm, more preferably in the range of 10⁻² to 10⁴ Ω·cm. Whenthe volume resistivity of the resin coating layer is more than 10⁵ Ω·cm,the charge up of toner tends to be generated and then toner stain on theresin coating layer easily occurs.

[0088] In the present invention, for adjusting the volume resistivity ofthe resin coating layer to a value within the above ranges, so thatother conductive fine particles may be dispersed and contained in theresin coating layer in addition to the above graphitized particles.

[0089] The conductive fine particles may be those having anumber-average particle diameter of 1 μm or less, more preferably 0.01to 0.8 μm. When the number average particle diameter of the conductivefine particles exceeds 1 μm, it becomes difficult to adjust the volumeresistivity of the resin coating layer to a lower value. Therefore,toner stain on the resin coating layer to be caused by the charge up oftoner tends to occur.

[0090] Conductive fine particles which can be used in the presentinvention include, for example, carbon blacks such as furnace black,lamp black, thermal black, acetylene black, and channel black; metaloxides such as titanium oxide, tin oxide, zinc oxide, molybdenum oxide,potassium titanate, antimony oxide, and indium oxide; metals such asaluminum, copper, silver, and nickel; and inorganic fillers such asgraphite, metal fiber, and carbon fiber.

[0091] For increasing the effects of the present invention, it ispreferable that spherical particles are further dispersed in the resincoating layer that constitutes the developer carrier of the presentinvention, which provide the unevennesses to the surface of the resincoating layer together and disperse such particles.

[0092] The spherical particles allow the resin coating layer surface ofthe developer carrier to retain a uniform surface roughness and also tohave an improved abrasion resistance. Furthermore, even in the casewhere the surface of the resin coating layer has been abraded, a littlechange may be only caused on the surface roughness of the coating layer.Therefore, it is advantageous in that the surface of the resin coatinglayer is hardly stained and fused with toner.

[0093] The number-average particle size of spherical particles to beused in the present invention is in the range of 1 to 30 μm, preferablyin the range of 2 to 20 μm.

[0094] When the number-average particle size of the spherical particlesis less than 1 μm, it is not preferable because of the followingreasons. That is, the effects of providing the surface of the resincoating layer with uniform roughness and increasing the abrasionresistance thereof may be insufficient. In this case, therefore, itbecomes insufficient to uniformly charge the developer. In addition, thecharge up of toner and toner stain and toner fusion on the resin coatinglayer are generated as the resin coating layer wears, resulting in adeterioration of ghost and a decrease in image density. When thenumber-average particle size of the spherical particles is more than 30μm, it is not preferable because of the following reasons. That is, anexcess increase in roughness of the surface of the resin coating layeroccurs. As a result, a sufficient charging of toner is hardly attainedwhile causing a decrease in mechanical strength of the coating layer.

[0095] The true density of spherical particles to be used in the presentinvention is preferably 3 g/cm³ or less, more preferably 2.7 g/cm³ orless, and still more preferably 0.9 to 2.3 g/cm³. In other words, whenthe true density of spherical particles exceeds 3 g/cm³, it is notpreferable because of the following reason. That is, the dispersibilityof spherical particles in the resin coating layer becomes insufficient,so that the surface of the resin coating layer is hardly provided with auniform roughness, resulting in insufficient charging of toner and aninsufficient strength of the coating layer.

[0096] Furthermore, when the true density of spherical particles is lessthan 0.9 g/cm³, it is not preferable because of an insufficientdispersibility of spherical particles in the coating layer.

[0097] The term “spherical” for the spherical particles to be used inthe present invention means that the ratio of longer axis/minor axis ofparticle in a particle projected image is almost in the range of 1.0 to1.5. In the present invention, preferably, the particles to be used maybe those with such a ratio of 1.0 to 1.2.

[0098] When the ratio of longer axis/minor axis of spherical particle ismore than 1.5, it is not preferable in terms of uniform charging totoner and the strength of resin coating layer. That is, thedispersibility of spherical particles in the resin coating layerdecreases and the surface roughness of the resin coating layer becomesuneven.

[0099] The spherical particles to be used in the present invention arenot specifically limited and may be any particles well known in the art,but they may be, for example, spherical resin particles, spherical metaloxide particles, and spherical carbonized product particles.

[0100] The spherical resin particles are those obtained by suspensionpolymerization, dispersion polymerization, or the like. The sphericalresin particles are capable of providing the resin coating layer with anappropriate surface roughness even by the addition of a small amountthereof. Furthermore, the spherical resin particles make the surfaceform of the resin coating layer uniform. Therefore, among the sphericalparticles described above, the spherical resin particles can bepreferably used. Materials for preparing such spherical resin particlesinclude acrylic resin particles such as polyacrylate andpolymethacrylate, polyamide resin particles such as nylon, polyolefinresin particles such as polyethylene and polypropylene, silicon resinparticles, phenol resin particles, polyurethane resin particles, styreneresin particles, and benzoguanamine particles. Alternatively, resinparticles obtained by pulverization may be used after subjecting them tothermal or physical treatment for making the particles into sphericalform.

[0101] In addition, an inorganic substance may be attached on thesurface of the above spherical particles or fixed thereon. Such aninorganic substance may be oxide such as SiO₂, SrTiO₃, CeO₂, CrO, Al₂O₃,ZnO, or MgO; nitride such as Si₃N₄; carbide such as SiC; or sulfide orcarbonate such as CbrO₄, BaSO₄, or CaCO₃. These inorganic substances maybe treated with a coupling agent.

[0102] The inorganic substance treated with the coupling agent can bepreferably used, especially for the purposes of improving theadhesiveness between the spherical particles and the coating resin,providing hydrophobic properties to the spherical particles, and so on.Such a coupling agent may be selected from, for example, silane couplingagents, titanium coupling agents, and zilcoaluminate coupling agents.More specifically, the silane coupling agents include hexamethyldisilazane, trimethyl silane, trimethyl chlorosilane, trimethylethoxysilane, dimethyl dichlorosilane, methyl trichlorosilane,allyldimethyl chlorosilane, allylphenyl dichlorosilane, benzyldimethylchlorosilane, bromethyl dimethylchlorosilane, a-chloroethyltrichlorosilane, β-chloroethyl trichlorosilane, chloromethyldimethylchlorosilane, triorganosilyl mercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethyl acetoxysilane,dimethyldiethoxy silane, dimethyldimethoxy silane, diphenyldiethoxysilane, hexamethyl disiloxane, 1,3-divinyl tetramethyl disiloxane, and1,3-diphenyl tetramethyl disiloxane, and also dimethyl polysiloxanehaving 2 to 12 siloxane units per molecule and a hydroxyl group bondedto one silicon atom on each unit located on the terminal of themolecule.

[0103] Consequently, by adhering or fixing the inorganic substance onthe surface of the spherical resin particles, it becomes possible toimprove the dispersibility of particles into the resin coating layer,the uniformity of the surface of the coating layer, the stain resistanceof the coating layer surface, the charging property for the toner, theabrasion resistance of the coating layer, and so on.

[0104] Furthermore, the spherical particles to be used in the presentinvention may preferably have conductivities because of the followingreason. That is, by providing the spherical particles withconductivities, electrical charges hardly accumulate on the surface ofparticles. Therefore, it becomes possible to decrease toner adhesion andto improve the charging properties for toner.

[0105] In the present invention, in terms of the conductivity ofspherical particles, the volume resistivity of particles may bepreferably 10⁶ Ω·cm or less, more preferably 10⁻³ to 10⁶ Ω·m. When thevolume resistivity of spherical particles is more than 10⁶ Ω·cm, it isnot preferable because of the following reason. That is, the surface ofthe resin coating layer is worn, so that the stain or fusion of theresin coating with toner easily occurs around the spherical particlesexposed on the surface of the resin coating layer. As a result, It maybe difficult to charge the toner immediately and uniformly.

[0106] In the resin coating layer used in the present invention, foradjusting its charging ability to toner, a charge control agent may beadditionally provided. The charge control agent may be selected from,for example, nigrosine or modified products thereof with fatty acidmetal salt, and so on; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphtosulfonate or tetrabutyl ammoniumtetrafluoroborate, or analogs thereof, which are onium salts such asphosphonium salt or lake pigments thereof (lake agents includephosphotungstenic acid, phosphomolybdic acid, phospotungsten molybdicacid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide,and so on); and metal salts of higher fatty acids; diorgano tin oxidessuch as butyl tin oxide, dioctyl tin oxide, and dicyclohexyl tin oxide;diorgano tin borates such as dibutyl tin borate, dioctyl tin borate, anddicyclohexyl tin borate; guanidines; imidazole compounds; fluorocarbonresins; polyamide resins; and nitrogen-containing acrylic resins.

[0107] Next, description will be made of a structure of a developercarrier according to the present invention. The developer carrieraccording to the present invention has a substrate and a resin coatinglayer formed on a surface of the substrate.

[0108] Shapes of the substrate include a cylindrical shape, a columnarshape, a belt shape, and the like. In the case of using a developingmethod with non-contact to a photosensitive drum, a metal cylindricalmember is preferably used, and specifically, a metal cylindrical tube ispreferably used. Preferably used as the metal cylindrical tube isnon-magnetic one made of mainly stainless steel, aluminum, an alloythereof, and the like.

[0109] Further, as the substrate in the case of using a developingmethod with direct contact to a photosensitive drum, preferably used isa columnar member formed by arranging a layer structure containingrubber such as urethane, EPDM, or silicone or elastomer around a metalcored bar. Further, in a developing method with the use of a magneticdeveloper, a magnet roller having a magnet arranged therein or the likeis arranged in a developer carrier in order to magnetically attract andhold the developer onto the developer carrier. In this case, it may bethat: the substrate with a cylindrical shape is used; and the magnetroller is arranged therein.

[0110] Hereinafter, description will be made of a structure of the resincoating layer of the developer carrier according to the presentinvention. FIGS. 1 to 4 each are a sectional schematic diagram showing apart of the developer carrier according to the present invention. Ineach of FIGS. 1 to 4, a resin coating layer 17, which is formed bydispersing graphitized particles a with a specific degree ofgraphitization and a specific hardness in coating resin b, is laminatedon a substrate 16 comprised of a metal cylindrical tube.

[0111]FIG. 1 shows a state in which the graphitized particles a aredispersed in the coating resin b. The graphitized particles a contributeto formation of relatively small unevenness and providing conductivityproperty with respect to a surface of the resin coating layer 17,release property and electrical charge-providing property with respectto a toner, and the like.

[0112]FIG. 2 shows a structure in which: the graphitized particles aform relatively large unevenness on the surface of the resin coatinglayer 17; and further, the coating resin b is doped with conductive fineparticles c in addition to the graphitized particles a to therebyenhance conductivity. The conductive fine particles c themselves hardlycontribute to the substantial formation of unevenness. However, not onlythe conductive fine particles c but also other solid particles are addedto the coating resin b in purpose of forming minute unevenness to thesurface of resin coating layer 17.

[0113]FIG. 3 is a model diagram in which spherical particles d arefurther added into the coating resin b in order to form relatively largeunevenness on the surface of the resin coating layer 17. In the figure,the graphitized particles a form small unevenness on the surface of theresin coating layer 17. Such a structure is effective in the case whereit is used in a developing device in which a developer regulating memberis elastically made in press-contact with a developer carrier (through atoner). That is, the spherical particles d on the surface of the resincoating layer 17 regulate a press-contact force of an elastic regulatingmember, and the graphitized particles a form small unevenness, tothereby also play a part of adjusting: the opportunity of contactcharging between the toner and the coating resin b and graphitizedparticles a; and the release characteristics of the toner with respectto the resin coating layer surface.

[0114] In FIG. 4, both the graphitized particles a and the sphericalparticles d contribute to the formation of unevenness on the surface ofthe resin coating layer 17. This embodiment may be implemented in, forexample, the case where the spherical particles d are made to have otherfunctions such as conductivity, electrical charge-providing property,and abrasion resistance in addition to providing unevenness.

[0115] As described above, according to the present invention, therespective particle diameters of the graphitized particles, theconductive fine particle, and the spherical particles are adjusted inresponse to the additional functions required of the developer carrierand the developing systems. Thus, the resin coating layer can be formedfor each of the above-mentioned forms.

[0116] Next, the constituent ratio of the respective components thatconstitute the resin coating layer is explained. This constituent ratiois a particularly preferable range in the present invention, but thepresent invention is not limited to the range.

[0117] As to the content of the graphitized particles dispersed in theresin coating layer, when the content is preferably in the range of 2 to150 parts by weight, more preferably in the range of 4 to 100 parts byweight, with respect to 100 parts by weight of coating resin, the effectof maintenance of a surface shape of a developer carrier and ofelectrical charge-providing to the toner is further exhibited. In thecase where the content of the graphitized particles is less than 2 partsby weight, the effect of the addition of the graphitized particles issmall; on the other hand, in the case where the content exceeds 150parts by weight, adhesion property of the resin coating layer becomestoo low, which may lead to degradation of abrasion resistance.

[0118] As to the content of the conductive fine particles that may becontained in the resin coating layer together with the graphitizedparticles, in the case where the content is preferably 40 parts or lessby weight, more preferably 2 to 35 parts by weight, with respect to 100parts by weight of coating resin, this is preferable because the volumeresistivity can be adjusted to the above-mentioned desired value withoutdamaging other physical properties required for the resin coating layer.

[0119] In the case where the content of the conductive fine particlesexceeds 40 parts by weight, the lowering of strength of the resincoating layer is recognized, which is not preferable.

[0120] In the case where spherical particles are contained in the resincoating layer in combination with the graphitized particles, when thecontent of the spherical particles is preferably in the range of 2 to120 parts by weight, more preferably in the range of 2 to 80 parts byweight, with respect to 100 parts by weight of coating resin. As aresult, a particularly preferable effect is obtained in terms of themaintenance of the surface roughness of the resin coating layer and theprevention of contamination by toner and scattering of toner. There is acase where, when the content of the spherical particles is less than 2parts by weight, the effect of the addition of the spherical particlesis small while, when the content exceeds 120 parts by weight, chargingproperty of the toner becomes too low.

[0121] In the present invention, a charge controlling agent may becontained in the resin coating layer in combination with the graphitizedparticles and the like in order to adjust the charging property of thedeveloper carrier. In this case, the content of the charge controllingagent is preferably set to 1 to 100 parts by weight with respect to 100parts by weight of coating resin. The case of less than 1 part by weightdoes not exhibit the effect of charging controllability through theaddition; on the other hand, the case of more than 100 parts by weightleads to dispersion failure in the resin coating layer, which easilyinvites the reduction in film strength.

[0122] In the present invention, as to the roughness of the surface ofthe resin coating layer, an arithmetic mean roughness (hereinafterreferred to as “Ra”) is preferably 0.3 to 3.5 μm, more preferably 0.5 to3.0 μm. In the case where Ra of the surface of the resin coating layeris less than 0.3 μm, unevenness for sufficiently performing feeding of adeveloper may be difficult to be formed on the surface of the resincoating layer, which makes the developer amount on the developer carrierunstable, and also, which makes the abrasion resistance and tonercontamination-resistance of the resin coating layer insufficient.

[0123] In the case of Ra exceeding 3.5 μm, a feeding amount of thedeveloper on the developer carrier becomes too large. Thus, to charge tothe developer uniformly becomes difficult, and also, the mechanicalstrength of the resin coating layer may be lowered.

[0124] The thickness of the resin coating layer is preferably 25 μm orless, more preferably 20 μm less, and further more preferably 4 to 20 μmin order to make the thickness of the resin coating layer uniformly, butthe present invention is not limited to the above thickness. The abovethickness can be obtained by setting a sticking mass on the substrate toapproximately 4000 to 20000 mg/m² although depending on the materialused for the resin coating layer.

[0125] Next, description will be made of a developing device of thepresent invention which includes the above-mentioned developer carrierof the present invention, an image forming apparatus that includes thedeveloping device, and a process cartridge of the present invention.FIG. 5 is a schematic diagram of an embodiment of the developing deviceincluding the developer carrier according to the present invention inthe case of using a magnetic one-component developer as a developer. InFIG. 5, an electrophotographic photosensitive drum (photosensitivemember for electrophotography) 1 serving as an electrostatic latentimage-bearing member, which holds an electrostatic latent image formedby a known process, is rotated in a direction of an arrow B.

[0126] A developing sleeve 8 serving as a developer carrier is arrangedso as to face the electrophotographic photosensitive drum 1 with apredetermined gap therebetween. The developing sleeve 8 is rotated in adirection of an arrow A while carrying a one-component developer 4containing a magnetic toner which is supplied by a hopper 3 serving as adeveloper container, thereby feeding the developer 4 to a developingregion D as a nearest portion that faces the developing sleeve 8 on asurface of the photosensitive drum 1. As shown in FIG. 5, a magnetroller 5 having a magnet built-in is arranged in the developing sleeve 8in order to magnetically attract and hold the developer 4 onto thedeveloping sleeve 8.

[0127] The developing sleeve 8 used in the developing device of thepresent invention has a conductive coating layer 7 serving as a resincoating layer coated on a metal cylindrical tube 6 as a substrate. Astirring blade 10 for stirring the developer 4 is arranged in the hopper3. Reference numeral 12 denotes a gap that indicates that the developingsleeve 8 and the magnet roller 5 are in a non-contact state.

[0128] The developer 4 obtains frictional charging charge that enablesdeveloping of the electrostatic latent image on the photosensitive drum1 with friction among the magnetic toner and friction between thedeveloper 4 and the conductive coating layer 7 on the developing sleeve8. In FIG. 5, a magnetic regulating blade 2, which serves as a developerlayer thickness regulating member and is made of ferromagnetic metal, ishung down from the hopper 3 so as to face the developing sleeve 8 with agap width of about 50 to 500 μm from a surface of the developing sleeve8. The magnetic regulating blade 2 forms a layer of the developer 4which is fed to the developing region D and regulates the thickness ofthe layer. Magnetic lines from a magnetic pole Ni of the magnet roller 5concentrate on the magnetic regulating blade 2, whereby the thin layerof the developer 4 is formed on the developing sleeve 8. Note that, inthe present invention, a non-magnetic blade may be used instead of themagnetic regulating blade 2. It is preferable that the thickness of thethin layer of the developer 4 formed on the developing sleeve 8 asdescribed above is further thinner than the minimum gap between thedeveloping sleeve 8 and the photosensitive drum 1 in the developingregion D.

[0129] The developer carrier of the present invention is particularlyeffective when being incorporated in a developing device of a type inwhich an electrostatic latent image is developed with theabove-mentioned thin layer of a developer, namely, a non-contact typedeveloping device, but can be also applied to a developing device inwhich a thickness of a developer layer is equal to or thicker than theminimum gap between the developing sleeve 8 and the photosensitive drum1 in the developing region D, namely, a contact type developing device.The following description will be made taking the above-mentionednon-contact type developing device as an example for the sake ofbrevity.

[0130] In order to fly the one-component developer 4 containing themagnetic toner which is carried on the developing sleeve 8, a developingbias voltage is applied to the developing sleeve 8 by a developing biaspower source 9 serving as bias means. When a direct-current voltage isused as the developing bias voltage, it is preferable that a voltagehaving an intermediate value between a potential of an image portion(region where the developer 4 is adhered to be visualized) and apotential of a background portion of the electrostatic latent image isapplied to the developing sleeve 8. An alternating bias voltage may beapplied to the developing sleeve 8 to form in the developing region D avibrating electric field whose direction is reciprocally reversed inorder to increase a density of the developed image or enhance gradationproperty. In this case, it is preferable that the alternating biasvoltage, on which a direct-current voltage component having theintermediate value between the potential of the above developed imageportion and the potential of the background portion is superimposed, isapplied to the developing sleeve 8.

[0131] In the case where a toner is adhered to a high potential portionof an electrostatic latent image having a high potential portion and alow potential portion to be visualized, that is, the case of so-callednormal developing, a toner to be electrified with an opposite polarityto the polarity of the electrostatic latent image is used. In the casewhere a toner is adhered to the low potential portion of theelectrostatic latent image having the high potential portion and the lowpotential portion to be visualized, that is, the case of so-calledreversal developing, a toner to be electrified with the same polarity asthe polarity of the electrostatic latent image is used. The highpotential and the low potential are expressions relative to the absolutevalue. In both the cases, the developer 4 is electrified by frictionwith at least the developing sleeve 8.

[0132]FIGS. 6 and 7 each is a structural schematic diagram showinganother embodiment of a developing device according to the presentinvention.

[0133] In each of the developing devices shown in FIGS. 6 and 7, anelastic regulating blade (elastic regulating member) 11 comprised of anelastic plate made of a material having rubber elasticity, such asurethane rubber or silicone rubber, or a material having metalelasticity, such as phosphor bronze or stainless steel is used as adeveloper layer thickness regulating member for regulating the layerthickness of the developer 4 on the developing sleeve 8. The developingdevice in FIG. 6 has such a characteristic that the elastic regulatingblade 11 is in press-contact with the developing sleeve 8 in a forwarddirection with respect to a rotational direction thereof. The developingdevice in FIG. 7 has such a characteristic that the elastic regulatingblade 11 is in press-contact with the developing sleeve 8 in an oppositedirection with respect to the rotational direction thereof. In thedeveloping devices, the developer layer thickness regulating member iselastically in press-contact with the developing sleeve 8 through thedeveloper layer. Thus, the thin layer of the developer is formed on thedeveloping sleeve. Therefore, there can be formed on the developingsleeve 8 a developer layer which is further thinner than the developerlayer in the case of using the magnetic regulating blade explained withreference to FIG. 5.

[0134] Note that, in the developing devices in FIGS. 6 and 7, the otherbasic structures are the same as those of the developing device shown inFIG. 5, and the same reference symbols basically denote identical parts.

[0135] Each of FIGS. 5 to 7 schematically exemplifies the developingdevice according to the present invention at the utmost. It is needlessto say that the shape of the developer container (hopper 3), thepresence or absence of the stirring blade 10, the arrangement ofmagnetic poles, and the like each have various forms. Of course, theabove developing devices can be used also in developing that uses atwo-component developer containing a toner and a carrier.

[0136]FIG. 8 is a schematic diagram showing an example of a structure ofa developing device of the present invention in the case of using anon-magnetic one-component developer. In FIG. 8, the electrophotographicphotosensitive drum 1 as the image bearing member that bears anelectrostatic latent image formed by a known process is rotated in thedirection of an arrow B. The developing sleeve 8 as the developercarrier is constituted of the metal cylindrical tube (substrate) 6 andthe resin coating layer 7 formed on a surface thereof. Since thenon-magnetic one-component developer is used, a magnet is not arrangedinside the metal cylindrical tube 6. A columnar member may be usedinstead of the metal cylindrical tube.

[0137] The stirring blade 10 for stirring a non-magnetic one-componentdeveloper 4′ is provided in the hopper 3 serving as the developercontainer.

[0138] A roller 13, which is a developer supplying and stripping member,for supplying the developer 4′ to the developing sleeve 8 and strippingoff the developer 4′ that exists on the surface of the developing sleeve8 after developing, abuts against the developing sleeve 8. The supplyingand stripping roller 13 rotates in the same direction as that of thedeveloping sleeve 8, and thus, a surface of the supplying and strippingroller 13 moves in a counter direction with respect to the surface ofthe developing sleeve 8. Thus, the non-magnetic one-component developercontaining a non-magnetic toner which is supplied from the hopper 3 issupplied to the developing sleeve 8. The developing sleeve 8 rotates inthe direction of an arrow A while carrying the one-component developer4″, so that the non-magnetic one-component developer 4′ is fed to thedeveloping region D that faces the developing sleeve 8 on the surface ofthe photosensitive drum 1. As to the one-component developer carried onthe developing sleeve 8, a thickness of the developer layer is regulatedby the developer layer thickness regulating member 11 in press-contactwith the surface of the developing sleeve 8 through the developer layer.The non-magnetic one-component developer 4′ gains frictional chargingcharge which can be developed the electrostatic latent image on thephotosensitive drum 1 by friction with the developing sleeve 8.

[0139] It is preferable that the thickness of the thin layer of thenon-magnetic one-component developer 4′ formed on the developing sleeve8 is thinner than the minimum gap in the developing region D between thedeveloping sleeve 8 and the photosensitive drum 1 in a developingportion. The present invention is particularly effective for anon-contact type developing device that develops an electrostatic latentimage with the above-mentioned developer layer. However, the presentinvention can also be applied to a contact type developing device inwhich the thickness of the developer layer is thicker than the minimumgap between the developing sleeve 8 and the photosensitive drum 1 in thedeveloping portion. Note that the following description will be madetaking the non-contact type developing device as an example for the sakeof brevity.

[0140] In order to fly the non-magnetic one-component developer 4′containing the non-magnetic toner which is carried on the developingsleeve 8, a developing bias voltage is applied to the developing sleeve8 by the developing bias power source 9. When a direct-current voltageis used as the developing bias voltage, it is preferable that a voltagehaving an intermediate value between a potential of an image portion(region where the non-magnetic developer 4′ is adhered to be visualized)and a potential of a background portion of the electrostatic latentimage is applied to the developing sleeve 8. An alternating bias voltagemay be applied to the developing sleeve 8 to form a vibrating electricfield in a developing portion whose direction is reciprocally reversedin order to increase a density of the developed image or enhancegradation property. In this case, it is preferable that the alternatingbias voltage on which a direct-current voltage component having theintermediate value between the above potential of the image portion andthe potential of the background portion is superimposed is applied tothe developing sleeve 8.

[0141] In the so-called normal developing in which a developer isadhered to a high potential portion of an electrostatic latent imagehaving the high potential portion and a low potential portion to bevisualized, a developer to be electrified with an opposite polarity tothe polarity of the electrostatic latent image is used. In the so-calledreversal developing in which a toner is adhered to the low potentialportion of the electrostatic latent image to be visualized, a developerto be electrified with the same polarity as the polarity of theelectrostatic latent image is used. Note that the high potential and thelow potential are expressions relative to the absolute value. In boththe cases, the non-magnetic one-component developer 4′ is electrifiedwith the polarity for developing the electrostatic latent image byfriction with the developing sleeve 8.

[0142] An elastic roller member made of resin, rubber, sponge, or thelike is preferable as the developer supplying and stripping member 13.Instead of the elastic roller, a belt member or a brush member may alsobe used as the stripping member. The developer, which has not movedthrough developing to the photosensitive member 1, is once stripped offfrom the sleeve surface by means of the developer supplying andstripping member 13, whereby the developer is prevented from being fixedon the sleeve, and the charging of the developer is made uniform.

[0143] In the case where the supplying and stripping roller 13 comprisedof the elastic roller is used as the developer supplying and strippingmember, a peripheral speed of the supplying and stripping roller 13 ispreferably 20 to 120%, more preferably 30 to 100%, with respect to aperipheral speed of 100% of the developing sleeve 8 when the surface ofthe roller 13 rotates in the counter direction with respect to thedeveloping sleeve 8.

[0144] In the case where the peripheral speed of the supplying andstripping roller 13 is less than 20%, the supply of the developer isinsufficient, and following property of a solid image lowers, whichbecomes the cause of a ghost image. In the case where the peripheralspeed exceeds 120%, the supply of the developer is increased, whichbecomes the cause of regulation failure of the thickness of thedeveloper layer and fog due to a shortage of a charging amount, andfurther, a toner is easily damaged, which is apt to become the cause offog due to toner deterioration and toner fusion.

[0145] In the case where the rotational direction on the surface of thesupplying and stripping roller 13 is the same (forward) with respect tothe rotational direction on the surface of the developing sleeve, theperipheral speed of the supplying roller is preferably 100 to 300%, morepreferably 101 to 200%, with respect to the peripheral speed of thesleeve in terms of the above-mentioned toner supply amount.

[0146] It is more preferable in terms of stripping property andsupplying property that the rotational direction on the surface of thesupplying and stripping roller 13 is counter with respect to therotational direction on the surface of the developing sleeve.

[0147] A penetration amount of the developer supplying and strippingmember 13 with respect to the developing sleeve 8 is preferably 0.5 to2.5 mm from the viewpoint of the supplying and stripping properties ofthe developer.

[0148] In the case where the penetration amount of the developersupplying and stripping member 13 is less than 0.5 mm, the ghost is easyto occur due to insufficiency of stripping; on the other hand, in thecase where the penetration amount exceeds 2.5 mm, the toner damagebecomes large, which easily becomes the cause of the fusion and fog dueto toner deterioration.

[0149] In the developing device in FIG. 8, the elastic regulating blade11, which is made of a material having rubber elasticity, such asurethane rubber or silicone rubber, or a material having metalelasticity, such as phosphor bronze or stainless copper, is used as amember for regulating the thickness of the non-magnetic one-componentdeveloper 4′ on the developing sleeve 8. The elastic regulating blade 11is made in press-contact with the developing sleeve 8 while being keptin an opposite position to the rotational direction of the developingsleeve 8. Thus, a thinner developer layer can be formed on thedeveloping sleeve 8.

[0150] As the elastic regulating blade 11, preferably used is a memberwith a structure in which polyamide elastomer (PAE) is adhered to asurface of a phosphor bronze plate that can obtain a stable pressurizingforce in order to particularly obtain a stable regulating force andstable (negative) charging imparting property to a toner. For example, acopolymer of polyamide and polyether is given as the polyamide elastomer(PAE).

[0151] A contact pressure of the developer layer thickness regulatingmember 11 with respect to the developing sleeve 8 is preferably a linearpressure of 5 to 50 g/cm in the point that this can stabilize theregulation of the developer and suitably adjust the developer layerthickness.

[0152] When the contact pressure of the developer layer thicknessregulating member 11 is a linear pressure of less than 5 g/cm, theregulation of the developer is reduced, which is apt to become the causeof fog and toner leakage. When the contact pressure exceeds a linearpressure of 50 g/cm, the damage to the toner becomes large, which is aptto become the cause of deterioration of the toner and fusion of thetoner to the sleeve and blade.

[0153] The developer carrier of the present invention is particularlyeffective when it is applied to the above-mentioned device in which thedeveloper supplying and stripping member 13 and the developer layerthickness regulating member 11 are in press-contact with the developingsleeve 8.

[0154] That is, in the case where the developer supplying and strippingmember 13 and the developer layer thickness regulating member 11 are inpress-contact with the developing sleeve 8, such a usage environment isprovided in which wear and fusion of the developer occur more easily onthe surface of the developing sleeve 8 by the press-contacted members.Thus, the effect of the developer carrier according to the presentinvention, which has the resin coating layer excellent in durability forthe large number of sheets is effectively exhibited.

[0155] Next, description will be made with reference to FIG. 9 of anexample of an image forming apparatus that uses the developing device ofthe present invention which is exemplified in FIG. 7. First, a surfaceof a photosensitive drum 101 serving as an electrostatic latent imagebearing member is electrified with a negative polarity by means ofcontact (roller) charging means 119 serving as a primary charging means,and image scanning is performed through an exposure 115 of laser lightwhich serves as latent image forming means to thereby form a digitallatent image (electrostatic latent image) on the photosensitive drum101. Next, by means of a developing device (developing means) having adeveloping sleeve 108 as a developer carrier and an elastic regulatingblade 111 as a developer layer thickness regulating member, and thedeveloping sleeve 108 has a multipolar permanent magnet 105 includedtherein, the digital latent image is subjected to reversal developingwith a one-component developer 104 containing a magnetic toner in ahopper 103. As shown in FIG. 9, a conductive substrate of thephotosensitive drum 101 is grounded in a developing region D, and analternating bias, a pulse bias and/or a direct-current bias is appliedto the developing sleeve 108 by means of bias applying means 109. Next,when a recording material P is conveyed to a transferring portion, aback surface (opposite surface to the photosensitive drum side) of therecording material P is electrified by voltage applying means 114through contact (roller) transferring means 113 serving as transferringmeans. Thus, the developed image (toner image) formed on the surface ofthe photosensitive drum 101 is transferred onto the recording material Pby the contact transferring means 113. Then, the recording material P isseparated from the photosensitive drum 101, and is conveyed to a heatingand pressurizing roller fixing device 117 serving as fixing means. Thetoner image on the recording material P is subjected to a fixing processwith the fixing device 117.

[0156] The one-component developer 104 remaining on the photosensitivedrum 101 after the transferring step is removed by cleaning means 118including a cleaning blade 118a. In the case where the amount of theremaining one-component developer 104 is small, a cleaning step can beomitted. After being subjected to cleaning, the photosensitive drum 101is subjected to charge elimination by an erase exposure 116 as theoccasion demands. Thereafter, the above-mentioned steps are repeatedagain which start from the charging step with the contact (roller)charging means 119 serving as the primary charging means.

[0157] In the above series of steps, the photosensitive drum (namely,electrostatic latent image bearing member) 101 has a photosensitivelayer and the conductive substrate, and is rotated in an arrowdirection. The non-magnetic cylindrical developing sleeve 108 serving asthe developer carrier is rotated so as to move in the same direction asthat of the surface of the photosensitive drum 101 in the developingregion D. The multipolar permanent magnet (magnet roll) 105 serving asmagnetic field generating means is arranged so as not to be rotated inthe developing sleeve 108. The one-component developer 104 in thedeveloper container 103 is applied and carried on the developing sleeve108, and is imparted with, for example, minus triboelectric charge byfriction with the surface of the developing sleeve 108 and/or frictionamong the magnetic toner. Further, the elastic regulating blade 111 isprovided so as to elastically press the developing sleeve 108 andregulate the thickness of a developer layer with thinness (30 to 300 μm)and uniformity, thereby forming the developer layer thinner than a gapbetween the photosensitive drum 101 and the developing sleeve 108 in thedeveloping region D. By performing adjustment of a rotational speed ofthe developing sleeve 108, a surface speed of the developing sleeve 108is made equal substantially or close to a surface speed of thephotosensitive drum 101. In the developing region D, analternating-current bias or pulse bias as a developing bias voltage maybe applied to the developing sleeve 108 by means of the bias applyingmeans 109. It is sufficient that the alternating-current bias has f of200 to 4000 Hz and Vpp of 500 to 3000 V.

[0158] The developer (magnetic toner) in the developing region D movesto the electrostatic latent image side due to the action of anelectrostatic force on the surface of the photosensitive drum 101 and ofthe developing bias voltage such as the alternating-current bias orpulse bias.

[0159] A magnetic doctor blade made of iron or the like may be usedinstead of the elastic regulating blade 111. The description of theprimary charging means is made above using the charging roller 119 thatserves as the contact charging means, but contact charging means such asa charging blade or charging brush, and further, non-contact coronacharging means may also be used. However, the contact charging means ispreferable in the point that it generates less ozone through charging.Further, the description of the transferring means is made above usingthe contact transferring means such as the transferring roller 113, butnon-contact corona transferring means may also be used. However, thecontact transferring means is preferable also in the point that itgenerates less ozone through transfer.

[0160]FIG. 10 shows an embodiment of a process cartridge according tothe present invention. In the following description of the processcartridge, members, which have identical functions as those of thestructural members of the image forming apparatus explained withreference to FIG. 9, are described with the same reference symbols asthose in FIG. 9. The process cartridge of the present invention is onein which at least developing means and an electrostatic latent imagebearing member are integrally formed into a cartridge, and is structuredso as to be attachably detachable to a main body of an image formingapparatus (for example, copying machine, laser beam printer, andfacsimile).

[0161] In the embodiment shown in FIG. 10, there is exemplified aprocess cartridge 150 which is formed by integrating developing means120, the drum-shape electrostatic latent image bearing member(photosensitive drum) 101, the cleaning means 118 including the cleaningblade 118 a, and the contact (roller) charging means 119 serving as theprimary charging means. In this embodiment, the developing means 120includes the developing sleeve 108, the elastic regulating blade 111,the developer container 103, and the one-component developer 104containing the magnetic toner which is received in the developercontainer 103. A developing step is performed in the developing means120. That is, developing is performed by forming a predeterminedelectric field between the photosensitive drum 101 and the developingsleeve 108 with the developing bias voltage from the bias applying meanswith the use of the developer 104. The distance between thephotosensitive drum 101 and the developing sleeve 108 is very importantin order to suitably perform the developing step.

[0162] The above description is made of the embodiment in FIG. 10 inwhich the four structural elements of the developing means 120, theelectrostatic latent image bearing member 101, the cleaning means 118,and the primary charging means 119 are integrally formed into thecartridge. However, any embodiment may be adopted in the presentinvention as long as the embodiment is one in which at least twostructural elements of developing means and an electrostatic latentimage bearing member are integrally formed into a cartridge. Also, theremay be adopted an embodiment in which a cartridge is constituted ofthree structural elements of developing means, an electrostatic latentimage bearing member, and cleaning means, and an embodiment in which acartridge is constituted of three structural elements of developingmeans, an electrostatic latent image bearing member, and the primarycharging means. Alternatively, it is possible that the above-mentionedtwo structural elements and other structural elements are integrallyformed into a cartridge.

[0163] Next, description will be made of a developer to be used in thedeveloping device of the present invention. The developer to be used inthe present invention may be a one-component developer that mainlycontains toner (without carrier) or a two-component developer thatcontains toner and carrier. In addition, when the one-componentdeveloper is used in the present invention, such a developer may be amagnetic one-component developer in which toner is magnetic toner or anon-magnetic one-component developer in which toner is non-magnetictoner.

[0164] Typically, the toner is provided as fine powders prepared by thesteps of melting and kneading a binder resin, a mold-releasing agent, acharge control agent, a coloring agent, and so on together, solidifyingand pulverizing the mixture, and classifying the resulting powders toobtain fine powders with uniform particle size distribution. The binderresin used in the toner may be typically well-known ones.

[0165] For example, it is selected from polymer made from styrene andsubstituents thereof including styrene, α-methyl styrene, andp-chlorostyrene; styrene copolymers including styrene-propylenecopolymer, styrene-vinyltoluene copolymer, styrene-ethylacrylatecopolymer, styrene-butylacrylate copolymer, styrene-octylacrylatecopolymer, styrene-dimethylaminoethyl copolymer, styrene-methylmethacrylate copolymer, styrene-ethyl methacrylate copolymer,styrene-butyl methacrylate copolymer, styrene-diaminoethyl methacrylatecopolymer, styrene-vinylmethylether copolymer, styrene-vinylmethylketone copolymer, styrene-butadiene copolymer, styrene-isoprenecopolymer, styrene-maleic acid copolymer, and styrene-maleic acid estercopolymer; and polymethyl methacrylate, polybutyl methacrylate,polyvinyl acetate, polyethylene, polypropylene polyvinyl butyral,polyacrylic acid resin, rosin, denatured rosin, terpene resin, phenolresin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleumresin, paraffin wax, and carnauba wax singly or in combination.

[0166] In addition, the toner may contain pigments as a coloring agent.The pigments may be selected from carbon black, nigrosine dye, lampblack, sudan black SM, fast yellow G, benzidine yellow, pigment yellow,indofast orange, Irgazin red, paranitroaniline red, toluidine red,carmine FB, permanent bordeaux FRR, pigment orange R, lithol red 2G,lake red C, rhodamine FB, rhodamine B lake, methyl violet B lake,phthalocyanine blue, pigment blue, brilliant green B, phthalocyaninegreen, oil yellow GG, shaddock fast yellow CGG, Kayaset Y963, KayasetYG, shaddock fast orange RR, oil scarlet, orasol brown B, shaddock fastscarlet CG, and oil pink OP.

[0167] For providing the toner as magnetic toner, magnetic powders maybe contained in the toner. The magnetic powders may be selected fromsubstances to be magnetized by being placed in the magnetic field. Suchsubstances include powders of ferromagnetic metals such as iron, cobalt,and nickel, and alloys and compounds of magnetite, hematite, ferrite,and so on. The content of the magnetic powders is preferably in therange of 15 to 70% by mass with respect to the mass of toner.

[0168] For improving the mold-releasing characteristics and fixingproperty of the toner at the time of toner fixation, the toner maycontain wax. The waxes include paraffin wax and derivatives thereof,microcrystalline wax and derivatives thereof, fischer-tropsch wax andderivatives thereof, polyolefin wax and derivatives thereof, andcarnauba wax and derivatives thereof. The derivatives include oxides,block copolymers with vinyl monomers, and graft modified products. Inaddition, alcohol, fatty acid, acid amide, ester, ketone, hardenedcastor oil and derivatives thereof, vegetable wax, animal wax, mineralwax, petrolatum, and so on may be applicable.

[0169] If required, the charge control agent may be included in thetoner. Typically, there are two types of charge control agents known inthe art. One is a negative charge control agent and the other is apositive charge control agent. For controlling the toner in negativecharge, the effective materials include organic metal complexes andchelate compounds such as monoazo metal complex, acetylacetone metalcomplex, aromatic hydroxycarboxylic acid metal complex, and aromaticdicarboxylic acid metal complex. Furthermore, the negative chargecontrol agents include aromatic hydroxycarboxylic acids, aromatic mono-and poly-carboxylic acids, and metal salts thereof, anhydrates, esters,phenol derivatives such as bisphenol, and so on.

[0170] Furthermore, substances that positively-charge the toner includenigrosine or modified products thereof with fatty acid metal salt, andso on, quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphtosulfonate, or tetrabutyl ammoniumtetrafluoroborate, analogs thereof, which are onium salts such asphosphonium salt, lake pigments thereof (lake agents includephosphotungstenic acid, phosphomolybdic acid, phospotungsten molybdicacid, tannic acid, lauric acid, gallic acid, ferricyanide, ferrocyanide,and so on), and metal salts of higher fatty acids; diorgano tin oxidessuch as dibutyl tin oxide, dioctyl tin oxide, and dicyclohexyl tinoxide; diorgano tin borates such as dibutyl tin borate, dioctyl tinborate, and dicyclohexyl tin borate; guanidines; and imidazolecompounds.

[0171] If required, the toner may be externally added with fine powderssuch as inorganic fine powders for improving the fluidity of toner. Thefine powders may include inorganic fine powders such as metal oxidessuch as silica fine powders, alumina, titania, germanium oxide, andzirconium oxide; and carbides such as silicon carbide and titaniumcarbide; and nitrides such as silicon nitride and germanium nitride.

[0172] These fine powders can be used by subjecting them to organictreatment with organic silicon compound, titanium-coupling agent, or thelike. For instance, the organic silicon compound may be selected fromhexamethyl disilazane, trimethyl silane, trimethyl chlorosilane,trimethyl ethoxysilane, dimethyl dichlorosilane, methyl trichlorosilane,allyldimethyl chlorosilane, allylphenyl dichlorosilane, benzyldimethylchlorosilane, bromomethyl dimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyl trichlorosilane, chloromethyldimethylchlorosilane, triorganosilyl mercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethyl acetoxysilane,dimethylethoxy silane, dimethyldimethoxy silane, diphenyldiethoxysilane, hexamethyl disiloxane, 1,3-divinyl tetramethyl disiloxane, and1,3-diphenyl tetramethyl disiloxane, and also dimethyl polysioxanehaving 2 to 12 siloxane units per molecule and a hydroxyl group bondedto one silicon atom on each unit located on the terminal of themolecule.

[0173] It is also preferable that untreated fine powders may be treatedwith a nitrogen-containing silane coupling agent particularly in thecase of positive toner. Examples of a chemical agent for the treatmentinclude aminopropyl trimethoxysilane, aminopropyl triethoxysilane,dimethylaminopropyl trimethoxysilane, diethylaminopropyltrimethoxysilane, dipropylaminopropyl trimethoxysilane,dibutylaminopropyl trimethoxysilane, monobutylaminopropyltrimethoxysilane, dioctylaminopropyl trimethoxysilane,dibutylaminopropyl dimethoxysilane, dibutylaminopropylmonomethoxysilane, dimethylaminophenyl trimethoxysilane,trimethoxysilyl-γ-propylphenyl amine, trimethoxysilyl-γ-propylbenzylamine, trimethoxysilyl-γ-propyl piperidine,trimethoxysilyl-γ-propylmorpholine, trimethoxysilyl-γ-propyl imidazole,and so on.

[0174] A method of treating fine powders with the above silane couplingagent is, for example, (1) a spray method, (2) an organic solventmethod, and (3) an aqueous solution method. In general, the treatmentwith the spray method includes the steps of stirring pigments, sprayingan aqueous or solvent solution of the coupling agent on the pigments,and removing the moisture or solvent by drying it at a temperature ofabout 120 to 130° C. The treatment with the organic solvent methodincludes the steps of dissolving a coupling agent in an organic solvent(e.g., alcohol, benzene, or halogenated hydrocarbon) containinghydrolytic catalyst together with a small amount of water, dippingpigments therein, conducting solid-liquid separation with filtration orcompression, and drying at a temperature of about 120 to 130° C. Theaqueous solution method includes the steps of hydrolyzing about 0.5% ofa coupling agent in water or a water-solvent at a constant pH, dippingpigments therein, and conducting solid-liquid separation just as in thecase of the treatment with the organic solvent, followed by drying.

[0175] As organic treatment, it is also possible to use fine powderstreated with silicone oil. Preferable silicone oil is one having aviscosity of about 0.5 to 10,000 mm²/second at 25° C., more preferably 1to 1,000 mm²/second at 25° C. The silicone oils include, for example,methylhydrodiene silicone oil, dimethyl silicone oil, phenylmethylsilicone oil, chlorophenyl methylsilicone oil, alkyl denatured siliconeoil, fatty acid denatured silicone oil, polyoxyalkylene denaturedsilicone oil, and fluorine denatured silicone oil.

[0176] Furthermore, it is also preferable to treat the above finepowders with silicone oil having a nitrogen atom on its side chainparticularly in the case of positive toner. The treatment with siliconeoil may be performed as follows, for example. That is, inorganic finepowders are vigorously stirred under heating if required, and the abovesilicone oil or a solution thereof is sprayed on the inorganic finepowders or sprayed after being vaporized on the inorganic fine powders.Alternatively, the inorganic fine powders are made in slurry form inadvance, and silicone oil or a solution thereof is dropped into theslurry while stirring to easily treat the fine powders with siliconeoil. The silicone oil may be used independently or in the form ofmixtures of two or more kinds of oil, or used in combination or in theform of being subjected to multiple treatments. In addition, it may beused together with the treatment with the silane coupling agent.

[0177] The toner to be used in the present invention as described aboveis preferable when the toner is subjected to the treatments to make thetoner particles into spherical form and to smooth the surface of thetoner by means of various methods as the toner is provided with goodtransfer characteristics. Such methods include: for example, a method inwhich a device having blade or vane for stirring, liner or casing, andso on is used, and the surface of toner is flattened by a mechanicalforce or the toner is changed into spherical form at the time of passingthe toner through a minute space between the blade and liner; a methodof suspending toner in hot water to form the toner into spherical form;and a method of exposing the toner to the flow of hot air to make thetoner into spherical form.

[0178] As a method of making the Loner into spherical form, there is amethod of suspending a mixture mainly containing a monomer to beprovided as a toner binder resin in water and polymerizing the monomerto make toner. As typical methods, a polymerizable monomer, a coloringagent, a polymerization initiator, and optionally a cross linking agent,a charge control agent, a mold-releasing agent, and other additives maybe uniformly dissolved or dispersed to obtain a monomer composition,followed by dispersing the monomer composition into a continuous phasesuch as a water phase containing a dispersion stabilizer using asuitable stirrer so as to become appropriate particle size, followed byinitiating the polymerization thereof to obtain a developer having adesired particle size.

[0179] The developer to be used in the present invention may be used asa mixture of toner and carrier as a two-component developer. The carriermaterial may be selected from, for example, magnetic metals such asiron, nickel, and cobalt, and alloys thereof; or alloys containing rareearth elements; iron oxides such as hematite, magnetite, soft ferritesincluding manganese-zinc ferrite, nickel-zinc ferrite,manganese-magnesium ferrite, and lithium ferrite, and copper-zincferrite and the mixture thereof; glass, ceramic particles such assilicon carbide; resin powders; and resin powders containing magneticsubstance. Generally, the carrier material is used in the form of aparticulate substance having an average particle size of about 20 to 300μm.

[0180] For the carrier, the above particulate substance may be directlyused as carrier particles. Alternatively, the surface of particles ofthe particulate substance may be coated with a coating agent such assilicone resin, fluororesin, acryl resin, or phenol resin, for adjustingthe frictional charge quantity of toner and preventing toner spent tothe carrier.

[0181] Next, description will be made of Embodiment 2 according to thepresent invention.

[0182] This embodiment is characterized in that a resin coating layerthat constitutes a developer carrier comprises the above-mentionedgraphitized particles (ii) as graphitized particles and furthercomprises scaly or acicular graphite with a degree of graphitizationP_(B)(002), which is 0.35 or less and is lower than a degree ofgraphitization P(002) of the graphitized particles (ii). Hereinafter,description will be made of a structure of the resin coating layer inthe developer carrier according to the present invention. Thedescription of the same structures as those in Embodiment 1 is omitted.FIG. 12 schematically shows an example of the structure, in whichgraphitized particles 51, having specific degree of graphitization, andcircularity and scaly or acicular graphitized particles 52 used in thepresent invention, are respectively dispersed in a resin coating layer54 on an aluminum cylindrical substrate 56. In this case, thegraphitized particles 51 and the graphitized particles 52 contribute tounevenness formation on a surface of the resin coating layer 54. Thecombined use of the graphitized particles (ii) and the graphitizedparticles having lubricity can avoid adhesion and fusion of tonercomponents although being disadvantageous in terms of abrasionresistance.

[0183]FIG. 13 shows a structure in which: the graphitized particles 51and the graphitized particles 52 form relatively large unevenness on thesurface of the resin coating layer 54; and further, conductive fineparticles 53 are added into coating resin in addition to the graphitizedparticles 51 to enhance conductivity. The conductive fine particles 53themselves do not contribute to substantial formation of unevennessmuch. However, in the present invention, not only the conductive fineparticles 53 but also other solid particles are added to the coatingresin in purpose of forming minute unevenness to the surface of resincoating layer 17.

[0184]FIG. 14 shows a model in which spherical particles 55 are furtheradded into the binding resin in order to provide relatively largeunevenness on the surface of the resin coating layer 54, and thegraphitized particles 51 and the graphitized particles 52 form smallunevenness on the surface of the resin coating layer 54. Such astructure is effective when being used in a developing device in which adeveloper regulating member is elastically made into press-contact witha developer carrier (through a toner). That is, the spherical particles55 on the surface of the resin coating layer 54 regulate a press-contactforce of an elastic regulating member, and the graphitized particles 51form small unevenness. Thus, the spherical particles 55 also play a roleof adjusting the opportunity of contact charging between the toner andthe coating resin and graphitized particles 51 in the resin coatinglayer, and adjusting release characteristics of the toner with respectto the resin coating layer surface.

[0185] In FIG. 15, both the graphitized particles 51 and the sphericalparticles 55 contribute to unevenness formation on the surface of theresin coating layer 54. Such an embodiment may be implemented in, forexample, the case where the spherical particles 55 are made to haveother functions such as conductivity, electrical charge-providingproperty, and abrasion resistance in addition to providing unevenness.

[0186] The graphitized particles used in this embodiment are thegraphitized particles (ii) with a degree of graphitization P(002) of0.20 to 0.95 and an average circularity SF-1, which is an average valueof circularity and is obtained by the above expression (1), of 0.64 ormore.

[0187] As described above, the graphitized particles (ii) are added inorder to make the coating layer surface of the developer carrier holduniform surface roughness, and at the same time, to obtain such a statein which: change in surface roughness of the coating layer is small evenin the case where the coating layer surface is worn; and contaminationand fusion of the resin coating layer by the toner are hardly generated.Further, the graphitized particles exhibit an effect of enhancing theelectrical charging-providing property to the toner. Note that thegraphitized particles (ii) are as described above.

[0188] Further, it is desirable that a degree of graphitizationP_(B)(002) of the scaly or acicular graphite used in combination withthe graphitized particles with the degree of graphitization P(002)satisfies the following relationship:

P _(B)(002)≦P(002).

[0189] The case of P_(B)(002)>P(002) is not desirable because theabrasion resistance of the coating layer surface is damaged due to adecline of a hardness of the graphitized particles (ii).

[0190] Crystalline graphite is preferably used as the scaly or aciculargraphitized particles used in the present invention. The crystallinegraphite is broadly divided into natural graphite and artificialgraphite. The natural graphite is produced from the earth aftercompletely graphitized due to natural geothermal heat and an undergroundhigh voltage for a long term. The artificial graphite is obtained by,for example, hardening pitch coke with tar pitch or the like, burningand carbonizing the resultant once at about 1000 to 1300° C., immersingit in various types of pitch, then putting it into a furnace forgraphitization, and subjecting it to a process at a high temperature ofabout 2500 to 3000° C., through which carbon crystals are grown to bechanged into graphite. The graphite is pulverized and classified toobtain graphitized particles with a desirable particle diameter.Crystalline structures of the graphite belong to a hexagonal system anda rhombohedral system, and have complete layer structures. Thus, thegraphitized particles each have a scaly or acicular shape.

[0191] The purpose of adding the scaly or acicular graphitized particlescomprised of the crystalline graphite into the coating layer is mainlyto provide conductivity and lubricity to the resin coating layer tothereby reduce charge-up, sleeve ghost, and toner fusion. The particlesthemselves are inferior in point of abrasion resistance since they aresoft and apt to be sheared. However, in the present invention, theabove-mentioned graphitized particles with a degree of graphitizationP(002) of 0.20 to 0.95 are used in combination therewith in order tocompensate for the inferior point.

[0192] The degree of graphitization P_(B)(002) of the scaly or aciculargraphitized particles preferably satisfies P_(B)(002)≦0.35. When thedegree of graphitization P_(B)(002) exceeds 0.35, the lubricity andconductivity tend to be lowered. Thus, the toner charge-up and the tonerfusion to the coating layer in endurable uses become easy to beproduced. As a result, sleeve ghost, fog, and image quality such asimage density become easy to be deteriorated.

[0193] The scaly or acicular graphite used in the present invention havelubricating properties. Separately from this, lubricating particles maybe further added. The lubricating particles may be, for example,molybdenum disulfide, boron nitride, mica, graphite fluoride,silver-niobium selenide, calcium chloride-graphite, talc, fatty acidmetal salt such as zinc stearate, and so on. The lubricating particlesto be used may have preferably a number-average particle size of about0.2 to 20 μm, more preferably 1 to 15 μm. When the number-averageparticle size of the lubricating particles is less than 0.2 μm, it isnot preferable because sufficient lubricity is hardly obtained. When thenumber-average particle size of the lubricating particles is more than20 μm, it is not preferable in terms of the abrasion resistance of theresin coating layer.

[0194] In this embodiment, for increasing the effects of the presentinvention, it is preferable to disperse other conductive fine particlesand spherical particles as described in the first embodiment incombination into the resin coating layer that constitutes the developercarrier. In the case of using the spherical particles particularly inthe form of FIG. 14 or FIG. 15, it is preferable to use conductiveparticles among these particles. That is, by providing the particleswith conductivity, charges hardly accumulate on the surface of particlesbecause of the conductivity, so that the degree of toner adhesion can bedecreased and the electrical charge-providing property to toner can beincreased. The conductivity of particles at this time, as describedabove corresponds to the volume resistivity of particles of 10⁶ Ω·cm orless, preferably in the range of 10⁻³ to 10⁶ Ω·cm.

[0195] Furthermore, the true density of particles is preferably about3,000 kg/m³ or less. Even if the particles are conductive, when the truedensity of particles is too high, the dispersion state of particlesduring manufacturing tends to become uneven because of a largedifference between the true density of the particles and the truedensity of the coating resin and an increase in the addition amount ofthe particles for providing the resin coating layer surface with theabove roughness. Therefore, it is not preferable as the dispersion stateof the coating layer being formed also becomes uneven. When theparticles are spherical, the contact area with the developer regulatingmember or the like to be compressed can be decreased. Thus, it ispreferable because of an increase in sleeve rotation torque byfrictional force, a decrease in toner adhesion, and so on. Inparticular, in the case of using the conductive spherical particlesdescribed below, a more advantageous effect can be obtained.

[0196] That is, as a method of obtaining particularly preferableconductive spherical particles, for example, there is a method in whichspherical resin particles or meso-carbon micro beads are baked forcarbonization and/or graphitization to obtain spherical carbon particleshaving low density and good conductivity. Furthermore, the resins to beused as spherical resin particles include, for example, phenol resin,naphthalene resin, furan resin, xylene resin, divinyl benzene polymer,styrene-divinyl benzene copolymer, and polyacrylonitrile. Furthermore,the meso-carbon micro beads can be generally produced by washingspherical crystals generated in the process of baking middle pitch underheating with a large amount of a solvent such as tar, middle oil orquinoline.

[0197] As a method of obtaining more preferable conductive sphericalparticles, the method includes the steps of covering the surface ofspherial resin particles such as phenol resin, napthalene resin, furanresin, xylene resin, divinyl benzene polymer, styrene-divinyl benzenecopolymer, and polyacrylonitrile with bulk mesophase pitch by means of amechano-chemical method, and heating the covered particles under acidicatmosphere, followed by baking the particles in the inert atmosphere orin a vacuum for carbonization and/or graphitization to obtain conductivespherical carbon particles. The spherical carbon particles obtained bythis method is preferable because the crystallization of coated portionsof the spherical carbon particle obtained through the graphitization hasproceeded, so that the conductivity thereof can be increased.

[0198] The conductive spherical carbon particles obtained by each of theabove methods can be favorably used in the present invention because itis possible to adjust the conductivity of spherical carbon particles tobe obtained by changing the baking conditions in each of the abovemethods. Furthermore, for increasing the conductivity, the sphericalcarbon particles obtained by the above methods, depending on the cases,may be plated with a conductive metal and/or metal oxide as long as anextensive increase in true density of the conductive spherical particlesdose not involved.

[0199] In this embodiment, coarse particles may further be contained inthe resin coating layer. It is preferable that a number-average particlediameter of the coarse particles is 5 to 50 μm. The case where thenumber-average particle diameter of the coarse particles is less than 5μm is not preferable because the case provides the small effect offorming uniform unevenness to the surface of the resin coating layer,and causes wear of the resin coating layer which easily leads to thelowering of developer-transporting property. In the case of thenumber-average particle diameter exceeding 50 μm, since unevenness onthe surface of the resin coating layer is too large, regulation of thedeveloper is insufficient, and transporting property of a developer isnonuniform. Thus, streaks, density unevenness of image, and the like areeasy to be generated. Further, a frictional force applied on thedeveloper becomes strong, and the deterioration of the developer and thetoner contamination on the surface of the resin coating layer inendurable use become easy to occur. Also, the mechanical strength of theresin coating layer is reduced. Therefore, the above case is notpreferable.

[0200] The developer carrier according to the present invention ismainly constituted of a metal cylindrical tube serving as a substrateand a resin layer that coats the tube. Stainless steel and aluminum aremainly and suitably used for the metal cylindrical tube.

[0201] Next, the constituent ratio of the respective components thatconstitute the resin coating layer is described, and the ratio falls ina particularly preferable range in the present invention. As to theratio of the graphitized particles and the scaly or acicular graphitizedparticles which are contained in the resin coating layer, a preferableresult is provided in a range of the graphitized particles/scaly oracicular graphitized particles=1/10 to 10/1 in mass ratio. In the massratio of less than 1/10, there is a tendency that electricalcharge-proving property to toner is reduced, and the abrasion resistancemay be degraded, which is not preferable. In the case of the mass ratioexceeding 10/1, since lubricity of the film may be damaged, there is atendency that the toner contamination on the surface of the resincoating layer is easy to generate in use over a long term.

[0202] As to the content of the graphitized particles contained in theresin coating layer, although which is depending on the content of thescaly or acicular graphitized particles, when the content is preferablyin the range of 2 to 100 parts by weight or more preferably in the rangeof 2 to 80 parts by weight with respect to 100 parts by weight ofcoating resin, a particularly preferable result is provided. In the casewhere the content of the graphitized particles is less than 2 parts byweight, the effect of the addition of the graphitized particles issmall, and necessary convex portions are difficult to be formed on thesurface of the resin coating layer. On the other hand, in the case ofthe content exceeding 100 parts by weight, the adhesion property betweenthe graphitized particles and the resin coating layer is too low, whichmay result in deterioration of the abrasion resistance.

[0203] As to the content of the scaly or acicular graphitized particlescontained in the resin coating layer, which is although depending on theabove-mentioned content of the graphitized particles, when the contentis preferably in the range of 2 to 100 parts by weight or morepreferably in the range of 2 to 80 parts by weight with respect to 100parts by weight of coating resin, a particularly preferable result isprovided. In the case where the content of the scaly or aciculargraphitized particles is less than 2 parts by weight, the effect oflubricity is small, and the toner contamination tends to occur easily onthe coating layer surface. On the other hand, in the case of the contentexceeding 100 parts by weight, the adhesion property between the scalyor acicular graphitized particles and the resin coating layer is toolow, which may result in deterioration of the abrasion resistance.

[0204] As to the content of the coarse particles in the case of beingcontained in the resin coating layer, when the content is preferably inthe range of 2 to 120 parts by weight or more preferably in the range of2 to 80 parts by weight with respect to 100 parts by weight of coatingresin, a particularly preferable result is provided. In the case wherethe content of the coarse particles is less than 2 parts by weight, theeffect of the addition of the coarse particles is small, and necessaryconvex portions are difficult to be formed on surface of the resincoating layer. On the other hand, in the case of the content exceeding120 parts by weight, the adhesion property between the coarse particlesand the resin coating layer is too low, which may result indeterioration of the abrasion resistance.

[0205] As to the content of the lubricating particles in the case ofbeing contained in the resin coating layer, when the content ispreferably in the range of 5 to 120 parts by weight or more preferablyin the range of 10 to 100 parts by weight with respect to 100 parts byweight of coating resin, a particularly preferable result is provided.In the case where the content of the lubricating particles exceeds 120parts by weight, the lowering of the film strength is recognized. On theother hand, in the case of the content less than 5 parts by weight, thetoner contamination tends to occur easily on the surface of the resincoating layer in use for a long time or the like.

[0206] As to the content of the conductive fine particles in the case ofbeing contained in the resin coating layer, when the content ispreferably in the range of 40 parts by weight or less or more preferablyin the range of 2 to 35 parts by weight with respect to 100 parts byweight of coating resin, a particularly preferable result is provided.That is, the case where the content of the conductive fine particlesexceeds 40 parts by weight is not preferable because the lowering of thefilm strength is recognized.

[0207] The dispersion of the particles described above into a solutionof the coating resin is generally performed by the dispersing devicewell known in the art, such as a paint shaker, a sand mill, an attritor,a dinomill, or a perlmill, by use of beads. The following methods can bementioned as a method of forming a resin coating layer of the developercarrier. That is, a conductive support as a substrate is verticallyarranged in parallel to the direction along which a spray gun moves andis then rotated. The spray gun is moved upward at a constant speed whilekeeping a predetermined distance between the conductive support and thenozzle tip of the spray gun to apply paint in which the above materialsare dispersed to the surface of a substrate by means of an air spraymethod, resulting in a resin coating layer. Generally, in the air spraymethod, a coating layer with excellent dispersion can be obtained byusing fine particles of the paint in the droplet form in a stabilized.Then, it is dried and hardened at 150° C. for 30 minutes in a hightemperature drier machine, resulting in developer carrier having thesurface coated with a resin coating layer.

[0208] In the present invention, the volume resistivity of the resincoating layer on the developer carrier is 10⁴ Ω·cm or less, morepreferably in the range of 10³ to 10⁻² Ω·cm. When the volume resistivityof the coating layer is more than 10⁴ Ω·cm, the charge up of toner tendsto occur and the resin coating layer is easily stained with toner. Thevolume resistivity of the resin coating layer was measured by forming aresin coating layer of 7 to 20 μm in thickness on a polyethyleneterephthalate (PET) sheet of 100 μm in thickness and attaching afour-terminal probe to Rolester AP (manufactured by MitsubishiPetrochemical Co., Ltd.).

[0209] The layer thickness of the resin coating layer described above ispreferably 25 μm or less, more preferably 20 μm or less, still morepreferably in the range of 4 to 20 μm to obtain uniform layer thickness.According to the present invention, however, the layer thickness is notspecifically limited to the above. The layer thickness of the resincoating layer can be attained with an adhesion weight of about 4,000 to20,000 mg/m², although depending on the outer diameter of the substrateor the material of the resin coating layer.

[0210] Here, the method of measuring the physical properties withrespect to the present invention will be described below.

[0211] (1) The Degree of Graphitization p(002) of Graphitized Particles

[0212] The degree of graphitization p(002) is obtained by measuringlattice spacing d(002) obtained from an X-ray diffraction spectrum ofgraphitized particles using a powerful full-automatic X-ray diffractioninstrument (“MXP18” system) manufactured by Mac Science, Co., Ltd., andcalculation of the following equation.

d(002)=3.440−0.086(1−p(002)²)

[0213] Furthermore, CuKα is used as an X-ray source, while CuK β ray isremoved through a nickel filter for mesuring the grating space d(002).Then, the grating space d (002) is calculated from the peak positions ofC(002) and Si(111) diffraction patterns using high purity silicon as astandard material. The principal measuring conditions are as follows.

[0214] X-ray generator: 18 kW

[0215] Goniometer: horizontal type goniometer

[0216] Monochromatic meter: use

[0217] Tube voltage: 30.0 kV

[0218] Tube current: 10.0 mA

[0219] Measuring method: continuous magnetization method

[0220] Scan axis: 2θ/θ

[0221] Sampling space: 0.020 deg

[0222] Scan speed: 6.000 deg/min.

[0223] Divergence slit: 0.50 deg

[0224] Scattering slit: 0.50 deg

[0225] Light-receiving slit: 0.30 mm

[0226] (2) Indentation Hardness HUT[68] of Graphitized Particles

[0227] An indentation hardness HUT[68] is a value measured by a microhardness meter MZT-4 manufactured by Akashi Corporation using a diamondindenter shaped like a triangular pyramid with a facial angle of 68°with respect to the shaft and is represented by the following equation(2).

Indentation hardness HUT [68]=K×F/(h2)²   (2)

[0228] (wherein K: coefficient, F: test load, and h2: maximumindentation depth of an indenter)

[0229] A sample for the measurement is prepared by flattening thesurface of a resin coating layer of developer carrier by grinding itwith an abrasive tape (#2000) so as to expose graphitized particles inthe resin coating.

[0230] The indentation hardness HUT[68] of the graphitized particles ismeasured as follows. At first, the sample is fixed, while adjusting asight of the indenter at the graphitized particle of 10 μm or more insize, which is being exposed from the surface of the resin coating layerby grinding for measurement. Then, ten or more different graphitizedparticles in the same sample were subjected to the measurement and theaverage of the resulting values was calculated as an indentationhardness HUT[68] of the graphitized particles.

[0231] The principal measuring conditions are as follows.

[0232] The measurement is conducted by TEST MODE A. The “TEST MODE A” isa mode in which the load for squeezing into the sample is defined forthe measurement. The loads to be applied are classified into two loadsan initial load referred to as a standard load F0 and a test load F1 asa final load. At the time of measurement, after the indenter is broughtinto contact with the sample, the standard load is applied on thesample. Then, the indenter is squeezed into the sample by theapplication of the standard load. A point where the indenter has beensqueezed with the standard load is defined as a zero point of theindentation depth. The indentation depth h2 (maximum indentation depthof the indenter) after retaining the test load of the indenter isobtained by applying the test load on the indenter, while retaining fora defined retention time period the test load. The indentation hardnessHUT [68] is calculated using the following equation (3). $\begin{matrix}{{{Indentation}\quad {hardness}\quad {{HUT}\lbrack 68\rbrack}} = {K \times {\left\lbrack {({F1})^{0.5} - ({F0})^{0.5}} \right\rbrack^{2}/({h2})^{2}}}} & (3)\end{matrix}$

[0233] [wherein, F1: test load (mN), F0: standard load (mN), h2:indentation depth (μm) after retaining the test load of the indenter,and K: coefficient (K=2.972, coefficient of SI unit using triangularpyramid indenter, 68°)]

[0234] Furthermore, other measuring conditions are as follows.

[0235] Test load F1: 49.0 mN

[0236] Standard load F0: 4.9 mN

[0237] Indentation speed V: 1.00 μm/sec.

[0238] Retention time T2: 5 sec.

[0239] Discharge time T3: 5 sec.

[0240] The test load and the maximum indentation depth of the indenteris preferably within the ranges free of influences of the surfaceroughness of the coating layer and also the base substrate. In thepresent invention, the measurement is performed under the conditions inwhich the maximum indentation depth of the test-load indenter is about 1to 2 μm.

[0241] (3) Coefficient of Friction μs

[0242] The developer carrier is fixed on a horizontal place. Then, themeasurement is performed by bringing a brass slider (copper pyritetreated with hard chrome) of a surface property tester (Model: TribogearMuse Type 94i, manufactured by HEIDON, Co., Ltd.) into contact with thedeveloper carrier in the longitudinal direction of the carrier.Furthermore, the coefficient of friction μs is measured such that tendifferent measuring points are appropriately defined on the surface ofthe developer carrier and the average of the resulting values obtainedfrom the measurements on these different points is obtained.

[0243] (4) Average Degree of Circularity SF-1 of Particles

[0244] A multi-image analyzer (manufactured by Beckman Coulter, Co.,Ltd.) is used as a measurement device for efficiently analyzing thedegree of circularity of many particles.

[0245] The multi-image analyzer includes a device for measuring particlesize distribution by means of an electric resistance method incombination with a function of photographing an particle image with aCCD camera and a function of analyzing the obtained particle image.Specifically, measurement particles uniformly dispersed in anelectrolyte solution by ultrasonics or the like are detected in terms ofa change in electric resistance which is generated when the particlespass through an aperture of a multisizer provided as a device ofmeasuring a particle size distribution by means of an electricresistance method. In synchronization with the passage of the particles,a strobe light flashes to photograph a particle image with the CCDcamera. Subsequently, the particle image is loaded into a personalcomputer and is then binarized, followed by analyzing the binarizedimage.

[0246] The above device can be used to obtain the maximum length ML ofPythagorean theorem and the projection area A of the particle profileview, and then the degree of circularity with respect to each of 3000particles of 2 μm or more in particle size is calculated from thefollowing equation (4), followed by averaging the resulting values toobtain the average degree of circularity SF-1.

Degree of circularity=(4×A)/{(ML)²×π}  (4)

[0247] (5) Measurement of Particle Size of Toner

[0248] In 100 to 150 ml of an electrolyte solution, 0.1 to 5 ml of asurfactant (alkylbenzene sulfonate) is added, and thereafter, 2 to 20 mgof a measuring sample is added. The electrolyte solution, in which thesample is being suspended, is dispersed using an ultrasonic dispersingdevice for 1 to 3 minutes. Using a coulter counter multisizer(manufactured by Coulter Co., Ltd.), particle size distribution ofparticle size of 0.3 to 40 μm or the like is measured on the basis ofthe volume using an aperture according to a toner size of 17 μm or 100μm as appropriate. The number-average particle size and theweight-average particle size measured under such conditions wereobtained by computer processing. Furthermore, from the particle sizedistribution on the basis of number of particles, a cumulativepercentage of cumulative distribution of half the number-averageparticle size or less is calculated to obtain a cumulative value ofcumulative distribution of the ½-fold number-average particle size orless. Similarly, a cumulative percentage of cumulative distribution ofthe 2-fold weight-average particle size or more is calculated from theparticle size distribution on the basis of volume to obtain a cumulativevalue of cumulative distribution of the 2-fold weight average particlesize or more.

[0249] (6) Measurement of Arithmetic Mean Roughness (Ra) of the Surfaceof Developer Carrier

[0250] Based on the surface roughness defined in Japanese IndustrialStandard (JIS) B0601, using a surface roughness measuring instrument(Model: Surfcorder SE-3400, manufactured by Kosaka Laboratory Ltd.), ameasurement is performed on each of six points (three points in theaxial direction and two points in the peripheral direction) under themeasurement conditions in which a cutoff of 0.8 mm, an evaluation lengthof 4 mm, and a feed speed of 0.5 mm/sec to obtain the average value ofthe measurements.

[0251] (7) Measurement of Volume Resistivity of Resin Coating Layer

[0252] A resin coating film of 7 to 20 μm in thickness is formed on aPET sheet of 100 μm in thickness. A fall-of-potential type digital ohmmeter (manufactured by Kawaguchi Electric Works Co., Ltd.) is used foreach measurement on the basis of the ASTM standard (D-991-82) and JapanRubber Manufacturers' Association (JPARMA) standard SRIS (2301-1969).The ohm meter includes an electrode having four-terminal structure formeasuring the volume resistivity of conductive rubber or plastic.Furthermore, each measurement is performed at a temperature of 20 to 25°C. and a humidity of 50 to 60 RH %.

[0253] (8) Measurement of Particle Size of Conductive Particles HavingParticle Sizes of 1 μm or More

[0254] The particle size of conductive particles such as graphitizedparticles is measured using a leaser diffraction type particle sizedistribution measuring instrument (Model: Coulter “LS-130”, manufacturedby Coulter Co., Ltd.). For the measurement, a water system module isused and pure water is used as a measuring solvent. The inside of ameasuring system of the particle size distribution measuring instrumentis washed with pure water for about 5 minutes. Then, 10 to 25 mg ofsodium sulfite is provided as an anti-foaming agent and added in themeasuring system, followed by performing a background function.

[0255] Subsequently, 3 to 4 drops of a surfactant is added in 10 ml ofpure water and 5 to 25 mg of a measuring sample is added. The aqueoussolution in which the sample is suspended is dispersed by sonicationwith an ultrasonic dispersing device for about 1 to 3 minutes to obtaina sample solution. The resulting sample solution is gradually added inthe measuring system of the above measuring device. The concentration ofthe sample in the measuring system is adjusted such that PIDS on thescreen of the device becomes 45 to 55%, followed by conducting themeasurement to obtain the number-average particle size calculated fromthe number-based particle size distribution.

[0256] (9) Measurement of Particle Size of Conductive Particles HavingParticle Sizes of Less than 1 μm

[0257] The particle size of conductive particles is measured using anelectron microscope. The image is taken in 60,000-magnification. If itis difficult, the image is taken with low magnification at first and thephotograph is then printed while being magnified. On the photograph, theparticle size of first-order particles is measured. At this time, bothof major and minor axes are measured and the average thereof is definedas a particle size. The measurement is repeated for 100 samples, and theaverage particle size is defined on the basis of 50% value.

[0258] (10) Measurement of Film Thickness (Amount of Chipping) of ResinCoating Layer

[0259] The amount of chipping (film chipping) on the coating layer ismeasured using a laser sizer manufactured by KEYENCE CORPORATION. Usinga controller LS-5500 and a sensor head LS-5040T, a sensor part isadditionally fixed on a device on which a sleeve fixing jig and a sleevefeeding mechanism are mounted. From the average outer diameter of thesleeve, the measurement is performed. The measurement is performed oneach of 30 different points defined by division into 30 pieces in thelongitudinal direction of the sleeve. Furthermore, the measurement isalso performed on each of different 30 points after 90° rotation of thesleeve in the peripheral direction. Therefore, the measurements areperformed on 60 points in total to obtain the average of the wholemeasurements. The outer diameter of the sleeve is measured before theapplication of a resin coating layer, and also the outer diameters ofthe sleeve after the resin coating layer is formed and after theendurable usage period expires is measured. The difference between thesemeasurements is defined as a thickness of resin coating layer and theamount of chipping.

[0260] In the following description, the present invention will beexplained in detail by way of examples and comparative examples.However, the examples are only provided for exemplification, so that thepresent invention is not limited to the examples. Furthermore, in theexamples and the comparative examples, “%” and “part” are based on massunless otherwise specified.

EXAMPLE 1-1

[0261] As a raw material of graphitized particles, β-resin was extractedfrom coal tar pitch using a solvent fractionation. Then, the β-resin wasmade heavier with hydrogenation, followed by removing the solventsoluble fraction with toluene to obtain bulk meso-phase pitch. Theresulting bulk meso-phase pitch was pulverized and was then oxidized atabout 3009C in the air, followed by primary baking at 1,200° C. undernitrogen atmosphere for carbonization. Subsequently, the carbonizedproduct was subjected to a secondary baking at 3,000° C. under nitrogenatmosphere for graphitization, followed by classification. Consequently,graphitized particles A-1-1 having a number-average particle size of 6.5μm were obtained. The physical properties of the graphitized particlesare listed in Table 1-1. TABLE 1 1 Physical properties of particlesadded in resin coating layer Number-average Degree of IndentationParticle Baking particle size Lattice spacing graphitization Averagedegree of hardness type Raw material temperature (μm) d (002) (Å) p(002) circularity SF-1 HUT [68] A-1-1 Bulk mesophase 3000 6.5 3.36510.36 0.69 42 pitch particles A-1-2 Bulk mesophase 3300 6.3 3.3582 0.220.67 26 pitch particles A-1-3 Bulk mesophase 2200 6.6 3.4077 0.79 0.7052 pitch particles A-1-4 Bulk mesophase 3000 3.3 3.3664 0.38 0.69 39pitch particles A-1-5 Meso-carbon micro 2800 6.7 3.3603 0.27 0.72 38beads A-1-6 Meso-carbon micro 3200 6.4 3.3585 0.23 0.71 24 beads A-1-7Meso-carbon micro 2200 6.8 3.4063 0.78 0.73 45 beads A-1-8 Bulkmesophase 3000 13.2 3.3598 0.26 0.73 43 pitch particles A-1-9 Bulkmesophase 3000 19.7 3.3603 0.27 0.71 46 pitch particles a-1-1 Coke andtar 2800 6.7 3.3549 0.10 0.60 6 pitch a-1-2 Phenol resin 2200 6.4Incapable Incapable 0.86 78 particles measurement measurement a-1-3 Bulkmesophase 1800 6.7 3.4470 1.04 0.70 54 pitch particles a-1-4 Meso-carbonmicro 1800 6.5 3.4400 1.00 0.74 48 beads a-1-5 Coke and tar 2800 13.63.3547 0.09 0.58 7 pitch a-1-6 Bulk mesophase 1800 13.5 3.4435 1.02 0.7255 pitch particles a-1-7 Phenol resin 2200 9.5 Incapable Incapable 0.8881 particles measurement measurement

[0262] 200 parts of resol-type phenol resin solution (containing 50%methanol);

[0263] 60 parts of graphitized particles (A-1-1); and

[0264] 150 parts of methanol.

[0265] Glass beads of 1 mm in diameter were added as media particles ina mixture of the above materials and were then dispersed by a sand mill.Subsequently, the solid fraction in the resulting dispersion solutionwas diluted to 30% with methanol to obtain a coating solution.

[0266] Using the coating solution and a spray method, a resin coatingfilm was formed on an aluminum cylindrical tube having an outer diameterof 16 mmφ and an arithmetic mean roughness Ra of 0.3 μm prepared bygrinding. After that, the resin coating film was dried and hardened byheating in a direct drying furnace at 150° C. for 30 minutes to obtain adeveloper carrier B-1-1. The formulation and the physical properties ofthe resulting developer carrier B-1-1 are listed in Table 1-2. TABLE 1 2Formulation and physical properties of resin coating layer of developercarrier Structure of resin coating layer Other Examples and Graphitizedspherical Coefficient Film Volume Comparative Developer particlesparticles Conductive fine of friction thickness Ra resistivity Examplescarrier (parts) (parts) particles Coating resin μs (μm) (μm) (Ω · cm)Example 1-1 B-1-1 A-1-1 (60) — — Phenol resin (100) 0.17 11.5 1.12 0.67Example 1-2 B-1-2 A-1-2 (60) — — Phenol resin (100) 0.14 11.2 1.10 0.50Example 1-3 B-1-3 A-1-3 (60) — — Phenol resin (100) 0.23 11.1 1.14 1.57Example 1-4 B-1-4 A-1-4 (60) — — Phenol resin (100) 0.24 10.9 0.90 0.62Example 1-5 B-1-5 A-1-5 (60) — — Phenol resin (100) 0.16 11.4 1.16 0.72Example 1-6 B-1-6 A-1-6 (60) — — Phenol resin (100) 0.14 11.5 1.12 0.53Example 1-7 B-1-7 A-1-7 (60) — — Phenol resin (100) 0.22 11.2 1.17 1.51Example 1-8 B-1-8 A-1-8 (45) a-1-7 (8) Carbon black (5) Phenol resin(100) 0.19 15.6 2.15 0.98 Example 1-9 B-1-9 A-1-9 (45) a-1-7 (8) Carbonblack (5) Phenol resin (100) 0.18 17.2 2.56 1.05 Example 1-10 B-1-10A-1-1 (36) — Carbon black (5) Phenol resin (100) 0.22 16.4 0.98 1.74Example 1-11 B-1-11 A-1-2 (36) — Carbon black (5) Phenol resin (100)0.18 16.1 0.95 1.43 Example 1-12 B-1-12 A-1-3 (36) — Carbon black (5)Phenol resin (100) 0.28 16.7 1.00 4.89 Example 1-13 B-1-13 A-1-4 (36) —Carbon black (5) Phenol resin (100) 0.21 16.4 0.78 1.87 ComparativeC-1-1 a-1-1 (60) — — Phenol resin (100) 0.14 11.2 1.09 0.63 Example 1-1Comparative C-1-2 a-1-2 (60) — — Phenol resin (100) 0.40 11.5 1.10 70.8Example 1-2 Comparative C-1-3 a-1-3 (60) — — Phenol resin (100) 0.3711.8 1.15 41.5 Example 1-3 Comparative C-1-4 a-1-4 (60) — — Phenol resin(100) 0.36 11.4 1.11 39.8 Example 1-4 Comparative C-1-5 a-1-5 (45) a-1-7(8) Carbon black (5) Phenol resin (100) 0.18 15.7 2.22 0.94 Example 1-5Comparative C-1-6 a-1-6 (45) a-1-7 (8) Carbon black (5) Phenol resin(100) 0.37 15.9 2.19 3.75 Example 1-6 Comparative C-1-7 a-1-1 (36) —Carbon black (5) Phenol resin (100) 0.18 16.9 1.00 1.57 Example 1-7Comparative C-1-8 a-1-2 (36) — Carbon black (5) Phenol resin (100) 0.416.5 0.95 82.3 Example 1-8 Comparative C-1-9 a-1-3 (36) — Carbon black(5) Phenol resin (100) 0.37 16.8 1.01 59.6 Example 1-9

[0267] The developer carrier B-1-1 was mounted on an image formingapparatus (Model: LBP1710, manufactured by Canon Inc.) shown in FIG. 9.Here, the image forming apparatus had a developing device shown in FIG.7 and was equipped with charging means for a contact roller andtransferring means for the contact roller. A durability evaluation testof the developer carrier was performed for printing 15,000 sheets whilesupplying one-component developer. The one-component developer used wasone containing the following components.

[0268] 100 parts of styrene-acrylic resin;

[0269] 95 parts of magnetite;

[0270] 2 parts of aluminum complex of di-tertiary butyl salicylic acid;and

[0271] 4 parts of low-molecular weight polypropylene.

[0272] The above materials were mixed by a Henschel mixer and themixture was then dissolved, kneaded, and dispersed using a biaxialextruder. The kneaded product was cooled and was then roughly pulverizedwith a hammer mill. Furthermore, the roughly pulverized product waspulverized into fine powders using a mechanical powdering machine,followed by being subjected to classification using an airflowclassifier to obtain fine powders (toner particles) having anumber-average particle size of 6.0 μm. Subsequently, 1.2 parts ofhydrophobic colloidal silica treated with a silane coupling agent wasexternally added to 100 parts of the fine powders to obtain magnetictoner. The resulting magnetic toner was provided as the one-componentdeveloper.

[0273] (Evaluation)

[0274] A durability test was performed with respect to the followingevaluation items for evaluating each of the developer carriers of theexamples and the comparative examples.

[0275] An evaluation test was performed for evaluating image qualitieswith respect to image density, fogging, sleeve ghost, blotch, uniformityof half-tone image, and so on; the amount of charge on toner on thedeveloper carrier (Q/M); the transfer amount of toner (M/S); and theabrasion resistance of the resin coating layer. Each of the evaluationtest were conducted under the surroundings of normal-temperature andnormal-humidity (N/N, 20° C./60%), normal-temperature and low-humidity(N/L, 24° C./10%), and high-temperature and high-humidity (H/H, 30°C./80%), respectively.

[0276] The results are listed in Tables 1-3 and 1-4. As shown in thetables, good results were obtained for both the image qualities anddurability.

[0277] (1-1) Image Density

[0278] Using a reflection densitometer RD918 (manufactured by Macbeth),the density of black solid image portion obtained by solid printing wasmeasured with respect to each of five different points on the image. Theaverage of the total measurement results was defined as the imagedensity.

[0279] (1-2) Fogging Density

[0280] The reflectivity (D1) of a white solid portion of the imageformed on a sheet of recording paper was measured. Furthermore, thereflectivity (D2) of a blank of another sheet of the same recordingpaper was measured. Then, the difference between D1 and D2 (i.e., thevalue of D1−D2) was obtained with respect to each of five differentpoints. The average of the total measurement results was defined as thefogging density. The reflectivity was measured using TC-6DS(manufactured by Tokyo Denshoku).

[0281] (1-3) Sleeve Ghost

[0282] The position of developing sleeve obtained by developing animage, in which a white solid portion and a black solid portion wereadjacent to each other, was placed on a developing position at the timeof a subsequent turn of the developing sleeve so as to develop ahalf-tone image. Then, the difference in gradation emerged on thehalf-tone image was visually observed and was then evaluated on thebasis of the following criteria.

[0283] A: No difference in gradation was observed.

[0284] B: A slight difference in gradation was observed

[0285] C: A small difference in gradation was observed but practicallyallowable.

[0286] D: Practically controversial difference in gradation was observedover one lap of sleeve.

[0287] E: Practically controversial difference in gradation was observedover two laps of sleeve.

[0288] (1-4) Blotch (Image Defect)

[0289] Various kinds of images such as black solid, half-tone, and lineimages were formed. Image defects such as wave-like unevenness andblotch (dot-like unevenness), and defective toner coating on thedeveloping sleeve at the time of image formation were visually observedand the results of the observations were referenced to evaluate on thebasis of the following criteria.

[0290] A: Any defect could not be observed on the image and the sleeve.

[0291] B: A defect was slightly found on the sleeve, but substantiallyno defect was observed on the image.

[0292] C: A defect was observed on a half-tone image or black solidimage in the first sheet of the recording paper and also observed on thesleeve at first rotation of the sleeve cycle.

[0293] D: A defect was observed on the half-tone image or black solidimage, but practically allowable.

[0294] E: A practically controversial image defect was observed on thewhole black solid image.

[0295] F: A practically controversial image defect was not only observedon the black solid image but also observed on the white solid image.

[0296] (1-5) Uniformity of Half-Tone Image (Generation of White Streakor White Belt)

[0297] The resulting image was visually observed with respect to linearor belt-shaped streak extending in the direction of image formation tobe generated particularly in a half-tone image, followed by evaluatingon the basis of the following criteria.

[0298] A: Any defect was found in both the image and the sleeve at all.

[0299] B: A defect was slightly observed when the image was carefullyobserved, but it was hardly recognized at a glance.

[0300] C: A defect was slightly observed in the half-tone image, whileit was substantially no problem in the black solid image.

[0301] D: A streak was observed in the half-tone image, while it wasslightly observed in the black solid image.

[0302] E: The difference in gradation was also observed in the blacksolid image, but practically allowable.

[0303] F: A practically controversial difference in gradation wasobserved in the whole black solid image.

[0304] G: Low image density and the images having many streaks weredistinctly observed.

[0305] (1-6) The amount of charge on toner (Q/M) and the transfer amountof toner (MIS)

[0306] Toner carried on the developing sleeve was absorbed and collectedinto a cylindrical metal tube and a cylindrical filter. At this time,the amount of charge per unit mass Q/M (mC/kg) and the mass of toner perunit area M/S(dg/m²) were calculated from the amount of electrostaticcharge Q accumulated in a capacitor through the cylindrical metal tube,the mass M of the collected toner, and the area S from which the tonerwas absorbed, to be defined as the amount of charge on toner (Q/M) andthe transfer amount of toner (M/S), respectively.

[0307] (1-7) Abrasion Resistance of Resin Coating Layer

[0308] The arithmetic mean roughness (Ra) of the developer carriersurface before and after the durability test and the amount of chippingin the film thickness of the resin coating layer were measured. TABLE 13 Results of evaluating the durability on LBP-1710 (with respect toimage density, fogging, sleeve ghost, blotch, and uniformity ofhalf-tone image) Uniformity of half- En- Image density Fogging Sleeveghost Blotch tone image viron- 10,000 15,000 10,000 15,000 10,000 15,00010,000 15,000 10,000 15,000 ment Initial sheets sheets Initial sheetssheets Initial sheets sheets Initial sheets sheets Initial sheets sheetsEx- N/N 1.48 1.44 1.41 0.7 1.5 1.9 A A A A A A A A A ample H/H 1.45 1.401.36 0.6 1.6 1.8 A A A A A A A A B 1-1 N/L 1.51 1.42 1.37 1.3 1.9 2.1 AA A A A A A A B Ex- N/N 1.46 1.42 1.38 0.8 1.7 2.0 A A A A A A A A Bample H/H 1.41 1.37 1.32 1.1 1.9 2.1 A A A A A A A B B 1-2 N/L 1.50 1.441.39 1.1 1.8 2.2 A A A A A A A A B Ex- N/N 1.50 1.42 1.39 1.0 1.8 2.4 AA B A A A A A B ample H/H 1.46 1.42 1.38 0.8 1.9 2.3 A A A A A A A B B1-3 N/L 1.50 1.39 1.31 1.5 2.3 2.8 A B B A A B A B C Ex- N/N 1.44 1.391.35 0.7 1.7 2.1 A A B A A A A B B ample H/H 1.40 1.36 1.31 0.6 1.8 2.2A A B A A A A B C 1-4 N/L 1.49 1.38 1.30 1.1 2.2 2.7 A B C A A B A B CEx- N/N 1.47 1.43 1.40 0.8 1.5 2.0 A A A A A A A A A ample H/H 1.44 1.391.34 0.8 1.6 2.0 A A A A A A A A B 1-5 N/L 1.51 1.41 1.35 1.4 2.1 2.3 AA A A A A A A B Ex- N/N 1.47 1.41 1.37 0.9 1.8 2.1 A A A A A A A A Bample H/H 1.40 1.35 1.30 1.2 2.0 2.0 A A A A A A A B B 1-6 N/L 1.51 1.421.37 1.2 2.0 2.3 A A A A A A A A B Ex- N/N 1.51 1.41 1.37 1.1 2.0 2.5 AA B A A A A A B ample H/H 1.45 1.40 1.36 0.9 2.1 2.4 A A B A A A A B B1-7 N/L 1.48 1.37 1.30 1.5 2.4 2.9 A B B A A B A B C Com- N/N 1.36 1.070.92 1.6 2.4 2.9 A C D A C E B B F para- H/H 1.26 0.66 0.82 1.5 2.5 2.7B D E A D E C F G tive N/L 1.38 0.98 0.85 2.4 3.0 3.5 A E E B F F B F GEx- ample 1-1 Com- N/N 1.40 1.11 0.97 1.7 2.6 3.1 C E E B E F B D Epara- H/H 1.40 1.10 0.95 1.4 2.5 3.0 C D E A D E B E F tive N/L 1.230.96 0.82 2.5 3.1 3.6 D E E C F F C E G Ex- ample 1-2 Com- N/N 1.46 1.171.09 1.4 2.2 2.8 B C D A C D B C D para- H/H 1.40 1.13 1.04 1.0 2.2 2.6A C C A B C A B C tive N/L 1.42 1.05 0.97 2.0 2.5 3.0 C D E B D E C D EEx- ample 1-3 Com- N/N 1.46 1.15 1.36 1.6 2.3 2.9 B C D A C D B C Dpara- H/H 1.39 1.10 1.02 1.1 2.4 2.7 A C D A B C A B D tive N/L 1.431.04 0.95 2.1 2.7 3.1 C D E B D E C D E Ex- ample 1-4

[0309] TABLE 1 4 Results of evaluating the durability on LBP-1710 (withrespect to Q/M, M/S, and abrasion resistance) Q/M(mC/Kg) M/S(dg/m²)Abrasion resistance 10,000 15,000 10,000 15,000 Initial After durabilityRa Amount of chipping Environment Initial sheets sheets Initial sheetssheets Ra (μm) (μm) (μm) Example 1-1 N/N 17.0 17.3 17.4 1.45 1.37 1.321.12 1.07 1.6 H/H 16.2 15.9 15.5 1.41 1.30 1.26 1.12 1.04 2.0 N/L 17.317.5 17.6 1.52 1.36 1.32 1.12 1.09 1.4 Example 1-2 N/N 15.9 16.2 15.61.43 1.34 1.29 1.10 1.04 1.9 H/H 14.5 13.7 13.2 1.37 1.28 1.24 1.10 1.012.4 N/L 16.2 16.7 17.0 1.51 1.38 1.32 1.10 1.06 1.6 Example 1-3 N/N 17.216.9 16.5 1.47 1.36 1.32 1.14 1.12 1.2 H/H 16.5 16.0 15.6 1.43 1.31 1.271.14 1.11 1.6 N/L 17.4 16.3 15.9 1.53 1.32 1.27 1.14 1.13 1.0 Example1-4 N/N 17.5 16.7 15.9 1.30 1.23 1.19 0.90 0.86 1.9 H/H 16.6 13.8 13.11.26 1.21 1.15 0.90 0.83 2.4 N/L 17.7 16.0 15.7 1.33 1.19 1.16 0.90 0.881.7 Example 1-5 N/N 16.7 16.9 17.0 1.50 1.38 1.31 1.16 1.10 1.7 H/H 16.015.7 15.3 1.43 1.31 1.27 1.16 1.07 2.2 N/L 17.4 17.6 17.5 1.54 1.37 1.321.16 1.12 1.5 Example 1-6 N/N 15.7 15.9 15.2 1.44 1.32 1.27 1.12 1.052.1 H/H 14.2 13.3 13.0 1.36 1.26 1.22 1.12 1.01 2.6 N/L 16.0 16.4 16.51.53 1.37 1.31 1.12 1.07 1.6 Example 1-7 N/N 17.0 16.8 16.4 1.49 1.351.32 1.17 1.14 1.4 H/H 16.4 15.8 15.4 1.46 1.32 1.26 1.17 1.11 1.8 N/L17.2 16.2 15.7 1.56 1.31 1.25 1.17 1.14 1.2 Comparative N/N 14.0 11.98.5 1.38 1.05 0.87 1.09 0.72 6.9 Example 1-1 H/H 11.7 9.5 6.8 1.29 0.900.73 1.09 0.68 8.6 N/L 14.7 10.7 7.7 1.40 0.95 0.76 1.09 0.74 6.0Comparative N/N 17.6 12.6 9.5 1.47 1.11 0.96 1.10 1.09 0.9 Example 1-2H/H 16.7 12.1 9.2 1.37 0.99 0.90 1.10 1.08 1.1 N/L 17.2 10.6 7.5 1.620.97 0.84 1.10 1.10 0.7 Comparative N/N 17.2 13.4 10.4 1.45 1.15 1.001.15 1.13 1.0 Example 1-3 H/H 16.4 12.9 9.8 1.41 1.08 0.95 1.15 1.12 1.3N/L 17.9 11.8 8.9 1.50 1.01 0.90 1.15 1.14 0.9 Comparative N/N 17.0 13.110.2 1.43 1.13 0.97 1.11 1.08 1.1 Example 1-4 H/H 16.1 12.6 9.6 1.391.07 0.93 1.11 1.06 1.4 N/L 17.7 11.5 8.7 1.48 0.99 0.88 1.11 1.08 1.0

EXAMPLE 1-2 AND EXAMPLE 1-3

[0310] Graphitized particles A-1-2 and A-1-3 were obtained by the samemanufacturing method as that of the graphitized particles A-1-1 exceptthat the temperature of secondary baking was changed as shown in Table1-1 from one used in Example 1-1. The physical properties of thegraphitized particles A-1-2 and A-1-3 are listed in Table 1-1. Developercarriers B-1-2 and B-1-3 were obtained by the same manufacturing methodas that of Example 1-1 except that the graphitized particles A-1-2 andA-1-3 are used as graphitized particles of the resin coating layerinstead of A-1-1. The same evaluation test as Example 1-1 was performedwith the developer carriers B-1-2 and B-1-3. The formulation and thephysical properties of the resin coating layer of the resultingdeveloper carrier are listed in Table 1-2. The results of the evaluationtests are listed in Tables 1-3 and 1-4.

EXAMPLE 1-4

[0311] Graphitized particles A-1-4 having the number-average particlesize of 3.3 μm were obtained by the same manufacturing method as that ofthe graphitized particles A-1-1 except that the pulverization conditionsfor bulk mesophase pitch and the classification conditions after thesecond baking of the raw material used in Example 1-1 were changed. Thephysical properties of the graphitized particles A-1-4 are listed inTable 1-1. Developer carrier B-1-4 is obtained by the same manufacturingmethod as that of Example 1-1 except that the graphitized particlesA-1-4 are used as graphitized particles of the resin coating layerinstead of A-1-1. The same evaluation test as Example 1-1 was performedwith the developer carrier B-1-4. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 1-2. The results of the evaluation tests are listedin Tables 1-3 and 1-4.

EXAMPLE 1-5

[0312] As a raw material of graphitized particles, coal heavy oil washeated to obtain crude mesocarbon micro beads. The resulting crudemesocarbon micro beads were subjected to centrifugal separation,followed by washing and purifying with benzene and drying. Subsequently,the dried product was mechanically dispersed using an atomizer mill toobtain the meso-carbon micro beads. The meso-carbon micro beads weresubjected to a primary baking at 1,200°C. under nitrogen atmosphere forcarbonization, followed by being subjected to a second dispersion withthe atomizer mill. The resulting dispersed product was subjected to asecond baking at 2,800° C. under nitrogen atmosphere for graphitization,and was then classified. Consequently, graphitized particles A-1-5having a number-average particle size of 6.7 μm were obtained. Thephysical properties of the graphitized particles A-1-5 are listed inTable 1-1.

[0313] Developer carrier B-1-5 is obtained by the same manufacturingmethod as that of Example 1-1 except that the graphitized particlesA-1-5 are used as graphitized particles of the resin coating layerinstead of A-1-1. The same evaluation test as Example 1-1 was performedwith the developer carrier B-1-5. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 1-2. The results of the evaluation tests are listedin Tables 1-3 and 1-4.

EXAMPLE 1-6 AND EXAMPLE 1-7

[0314] Graphitized particles A-1-6 and A-1-7 were obtained by the samemanufacturing method as that of Example 1-5 except that the temperatureof the secondary baking for obtaining the graphitized particles inExample 1-5 was changed. The physical properties of the graphitizedparticles A-1-6 and A-1-7 are listed in Table 1-1.

[0315] Developer carriers B-1-6 and A-1-7 are obtained by the samemanufacturing method as that of Example 1-1 except that the graphitizedparticles A-1-6 and A-1-7 are used as graphitized particles of the resincoating layer instead of A-1-1. The same evaluation test as Example 1-1was performed with the developer carriers B-1-6 and B-1-7. Theformulation and the physical properties of the resin coating layer ofthe resulting developer carrier are listed in Table 1-2. The results ofthe evaluation tests are listed in Tables 1-3 and 1-4.

Comparative Example 1-1

[0316] As raw materials of graphitized particles, a mixture of coke andtar pitch was used. The mixture was kneaded at a temperature of over thesoftening point of the tar pitch and was then extruded by extrusion,followed by being subjected to a primary baking at 1,000°C. undernitrogen atmosphere for carbonization. In the resulting carbide, coaltar pitch was immersed. Then, the immersed product was graphitized by asecondary baking at 2,800° C. under nitrogen atmosphere. Subsequently,the mixture was pulverized and classified. Consequently, graphitizedparticles a-1-1 having a number-average particle size of 6.7 μm wereobtained. The physical properties of the graphitized particles a-1-1 arelisted in Table 1-1.

[0317] Developer carrier C-1-1 are obtained by the same manufacturingmethod as that of Example 1-1 except that the graphitized particlesa-1-1 are used as graphitized particles of the resin coating layerinstead of A-1-1. The same evaluation test as Example 1-1 was performedwith the developer carriers C-1-1. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 1-2. The results of the evaluation tests are listedin Tables 1-3 and 1-4.

Comparative Example 1-2

[0318] As a raw material of graphitized particles, spherical phenolresin particles were used. The particles were baked at 2,200° C. undernitrogen atmosphere, followed by classification. Consequently,graphitized particles a-1-2 having a number-average particle size of 6.4μm were obtained. The physical properties of the graphitized particlesa-1-2 are listed in Table 1-1.

[0319] Developer carrier C-1-2 are obtained by the same manufacturingmethod as that of Example 1-1 except that the graphitized particlesa-1-2 are used as graphitized particles of the resin coating layerinstead of A-1-1. The same evaluation test as Example 1-1 was performedwith the developer carriers C-1-2. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 1-2. The results of the evaluation tests are listedin Tables 1-3 and 1-4.

Comparative Example 1-3

[0320] Graphitized particles a-1-3 were obtained by the samemanufacturing method as that of the graphitized particles A-1-1 exceptthat the temperature of the secondary baking for obtaining thegraphitized particles in Example 1-1 was changed. The physicalproperties of the graphitized particles a-1-3 are listed in Table 1-1.Developer carrier C-1-3 is obtained by the same manufacturing method asthat of Example 1-1 except that the graphitized particles a-1-3 are usedas graphitized particles of the resin coating layer instead of A-1-1.The same evaluation test as Example 1-1 was performed with the developercarriers C-1-3. The formulation and the physical properties of the resincoating layer of the resulting developer carrier are listed in Table1-2. The results of the evaluation tests are listed in Tables 1-3 and1-4.

Comparative Example 1-4

[0321] Graphitized particles a-1-4 were obtained by the samemanufacturing method as that of the graphitized particles A-1-1 exceptthat the temperature of the secondary baking for obtaining thegraphitized particles in Example 1-5 was changed. The physicalproperties of the graphitized particles a-1-4 are listed in Table 1-1.Developer carrier C-1-4 is obtained by the same manufacturing method asthat of Example 1-1 except that the graphitized particles a-1-4 are usedas graphitized particles of the resin coating layer instead of A-1-1.The same evaluation test as Example 1-1 was performed with the developercarrier C-1-4. The formulation and the physical properties of the resincoating layer of the resulting developer carrier are listed in Table1-2. The results of the evaluation tests are listed in Tables 1-3 and1-4.

EXAMPLE 1-8

[0322] Graphitized particles A-1-8 having the number-average particlesize of 13.2 μm were obtained by the same manufacturing method as thatof the graphitized particles A-1-1 except that the pulverizationconditions for bulk mesophase pitch and the classification conditionsafter the second baking of the raw material used in Example 1-1 werechanged.

[0323] 200 parts of resol-type phenol resin solution (containing 50%methanol);

[0324] 45 parts of graphitized particles (A-1-8);

[0325] 5 parts of conductive carbon black;

[0326] 8 parts of spherical particles a-1-7 (carbonized particlesobtained by baking the phenol resin particles at 2,200° C.); and

[0327] 130 parts of methanol.

[0328] Glass beads of 1 mm in diameter were added as media particles ina mixture of the above materials and were then dispersed by a sand mill.Subsequently, the solid fraction in the resulting dispersion solutionwas diluted to 33% with methanol to obtain a coating solution.

[0329] Using the coating solution and a spray method, a resin coatingfilm was formed on an aluminum cylindrical tube having an outer diameterof 20 mmφ and an arithmetic mean roughness Ra of 0.4 μm prepared bygrinding. After that, the resin coating film was dried and hardened byheating in a direct drying furnace at 150° C. for 30 minutes to obtain adeveloper carrier B-1-8. The formulation and the physical properties ofthe resulting developer carrier B-1-8 are listed in Table 1-2.

[0330] The developer carrier B-1-8 was mounted on an image formingapparatus (Model: LBP1910, manufactured by Canon Inc.) shown in FIG. 9.Here, the image forming apparatus had a developing device shown in FIG.7 and was equipped with charging means for a contact roller andtransferring means for the contact roller. A durability evaluation testof the developer carrier was performed for printing 30,000 sheets whilesupplying one-component developer. The one-component developer used wasone containing the following components.

[0331] 100 parts of polyester resin;

[0332] 100 parts of magnetite;

[0333] 1 part of aluminum complex of di-tertiary butyl salicylic acid;and

[0334] 5 parts of low-molecular weight polypropylene.

[0335] The above materials were mixed by a Henschel mixer and themixture was then dissolved, kneaded, and dispersed using a biaxialextruder. The kneaded product was cooled and was then roughly pulverizedwith a hammer mill. Furthermore, the roughly pulverized product waspulverized into fine powders using a pulverizer with a jet airflow,followed by being subjected to classification using an airflowclassifier to obtain fine powders (toner particles) having anumber-average particle size of 5.8 μm. Subsequently, 1.2 parts ofhydrophobic colloidal silica treated with a silane coupling agent wasexternally added to 100 parts of the fine powders to obtain magnetictoner. The resulting magnetic toner was provided as the one-componentdeveloper.

[0336] (Evaluation)

[0337] A durability test was performed with respect to the followingevaluation items for evaluating each of the developer carriers of theexamples and the comparative examples.

[0338] An evaluation test was performed by the same method as that ofExample 1-1 for evaluating image qualities with respect to imagedensity, fogging, sleeve ghost, blotch, uniformity of half-tone, and soon; the amount of charge on toner on the developer carrier (Q/M); thetransfer amount of toner (M/S); and the abrasion resistance of the resincoating layer. In addition, the stain resistance of the resin coatinglayer of the developer carrier was evaluated as follows. In each ofevaluating items, the durability evaluations were performed under thesurroundings of normal-temperature and normal-humidity (N/N, 20°C./60%), normal-temperature and low-humidity (N/L, 24° C./10%), andhigh-temperature and high-humidity (H/H, 32° C./80%), respectively. Theresults are listed in Tables 1-5 and 1-6. As shown in the tables, goodresults were obtained for both the image qualities and durability.

[0339] (Stain Resistance of Resin Coating Layer)

[0340] The surface of developer carrier after the durability test wasobserved by magnifying by 200 times using a color laser 3D profilemicroscope manufactured by KEYENCE CORPORATION. The degree of tonerstain was evaluated on the basis of the following criteria.

[0341] A: Only a negligible amount of stain was observed.

[0342] B: A small amount of stain was observed.

[0343] C: Partial stain was observed.

[0344] D: Significant stain was observed. TABLE 1 5 Results ofevaluating the durability on LBP-1910 (with respect to image density,fogging, sleeve ghost, blotch, and uniformity of half-tone image)Uniformity of half- En- Image density Fogging Sleeve ghost Blotch toneimage viron- 15,000 30,000 15,000 30,000 15,000 30,000 15,000 30,00015,000 30,000 ment Initial sheets sheets Initial sheets sheets Initialsheets sheets Initial sheets sheets Initial sheets sheets Ex- N/N 1.501.47 1.44 0.8 1.0 1.2 A A A A A A A A A ample H/H 1.46 1.40 1.38 0.8 1.11.5 A A A A A A A A B 1-8 N/L 1.51 1.48 1.46 1.1 1.4 1.7 A A A A A A A AA Ex- N/N 1.51 1.45 1.44 1.5 2.0 2.4 A A A A A A A A A ample H/H 1.381.35 1.33 1.2 1.6 2.0 A A A A A A B B B 1-9 N/L 1.51 1.47 1.46 1.9 2.42.8 B A A A A A B A B Com- N/N 1.45 1.37 1.30 1.5 2.1 2.8 A A B A A A AB B para- H/H 1.31 1.28 1.17 1.4 2.6 2.8 A A B A A A A B D tive N/L 1.461.34 1.27 1.8 2.7 3.3 A B C A A B A B C Ex- ample 1-5 Com- N/N 1.45 1.391.20 1.8 2.5 3.1 B C D A C C A B C para- H/H 1.38 1.31 1.16 1.6 2.4 2.9A C D A B C B B C tive N/L 1.43 1.29 1.15 2.7 3.2 3.5 C D E B C D A C DEx- ample 1-6

[0345] TABLE 1 6 Results of evaluating the durability on LBP-1910 (withrespect to Q/M, M/S, abrasion resistance and stain resistance) abrasionresistance Q/M(mC/Kg) M/S(dg/m²) After Amount of 15,000 30,000 15,00030,000 Initial durability chipping Stain Environment Initial sheetssheets Initial sheets sheets Ra (μm) Ra (μm) (μm) resistance Example 1-8N/N 16.3 15.1 14.0 2.22 2.10 2.03 2.15 2.02 1.7 A H/H 15.2 14.1 13.02.11 1.98 1.91 2.15 1.97 2.0 A N/L 17.0 15.7 14.5 2.34 2.25 2.15 2.152.07 1.5 A Example 1-9 N/N 14.5 13.8 13.2 2.56 2.47 2.39 2.56 2.40 1.9 AH/H 13.8 13.0 12.4 2.39 2.28 2.18 2.56 2.36 2.2 B N/L 15.1 14.0 13.32.67 2.59 2.50 2.56 2.44 1.7 A Comparative N/N 13.2 11.3 10.0 2.20 1.891.68 2.22 1.97 2.8 B Example 1-5 H/H 11.7 9.8 7.9 2.04 1.69 1.49 2.221.89 3.4 D N/L 14.5 10.5 8.7 2.31 1.90 1.57 2.22 2.02 2.4 C ComparativeN/N 16.5 11.7 9.1 2.31 1.86 1.70 2.19 2.10 1.3 B Example 1-6 H/H 15.610.6 8.3 2.09 1.78 1.56 2.19 2.00 1.7 C N/L 17.1 11.2 7.9 2.40 1.76 1.542.19 2.06 1.2 D

EXAMPLE 1-9

[0346] Graphitized particles A-1-9 having the number-average particlesize of 19.7 μm were obtained by the same manufacturing method as thatof the graphitized particles A-1-1 except that the pulverizationconditions for bulk mesophase pitch and the classification conditionsafter the second baking of the raw material used in Example 1-1 werechanged. The physical properties of the graphitized particles A-1-9 arelisted in Table 1-1.

[0347] Developer carrier B-1-9 is obtained by the same manufacturingmethod as that of Example 1-8 except that the graphitized particlesA-1-9 are used as graphitized particles of the resin coating layerinstead of A-1-8. The same evaluation test as Example 1-8 was performedwith the developer carrier B-1-9. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 1-2. The results of the evaluation tests are listedin Tables 1-5 and 1-6.

Comparative Example 1-5

[0348] As raw materials of graphitized particles, a mixture of coke andtar pitch was used. The mixture was kneaded at a temperature of over thesoftening point of the tar pitch and was then extruded by extrusion,followed by being subjected to a primary baking at 1,000° C. undernitrogen atmosphere for carbonization. In the resulting carbide, coaltar pitch was immersed. Then, the immersed product was graphitized by asecondary baking at 2,800° C. under nitrogen atmosphere. Subsequently,the mixture was pulverized and classified. Consequently, graphitizedparticles a-1-5 having a number-average particle size of 13.6 μm wereobtained. The physical properties of the graphitized particles a-1-5 arelisted in Table 1-1.

[0349] Developer carrier C-1-5 are obtained by the same manufacturingmethod as that of Example 1-8 except that the graphitized particlesa-1-5 are used as graphitized particles of the resin coating layerinstead of A-1-8. The same evaluation test as Example 1-8 was performedwith the developer carriers C-1-5. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 1-2. The results of the evaluation tests are listedin Tables 1-5 and 1-6.

Comparative Example 1-6

[0350] Graphitized particles a-1-6 were obtained by the samemanufacturing method as that of the graphitized particles A-1-8 exceptthat the temperature of secondary baking was changed as shown in Table1-1 from one used in Example 1-8. The physical properties of thegraphitized particles a-1-6 are listed in Table 1-1. Developer carrierC-1-6 was obtained by the same manufacturing method as that of Example1-8 except that the graphitized particles a-1-6 are used as graphitizedparticles of the resin coating layer instead of A-1-8. The sameevaluation test as Example 1-1 was performed with the developer carriersC-1-6.

[0351] The formulation and the physical properties of the resin coatinglayer of the resulting developer carrier are listed in Table 1-2. Theresults of the evaluation tests are listed in Tables 1-5 and 1-6.

EXAMPLE 1-10

[0352] 200 parts of resol-type phenol resin solution (containing 50%methanol);

[0353] 36 parts of graphitized particles (A-1-1);

[0354] 5 parts of conductive carbon black; and

[0355] 120 parts of methanol.

[0356] Glass beads of 1 mm in diameter were added as media particles ina mixture of the above materials and were then dispersed by a sand mill.Subsequently, the solid fraction in the resulting dispersion solutionwas diluted to 35% with methanol to obtain a coating solution.

[0357] Using the coating solution and a spray method, a resin coatingfilm was formed on an aluminum cylindrical tube having an outer diameterof 32 mmφ and an arithmetic mean roughness Ra of 0.2 μm prepared bygrinding. After that, the resin coating film was dried and hardened byheating in a direct drying furnace at 150° C. for 30 minutes to obtain adeveloper carrier B-1-10. The formulation and the physical properties ofthe resulting developer carrier B-1-10 are listed in Table 1-2.

[0358] The developer carrier B-1-10 was mounted on an image formingapparatus (Model: IR8500, manufactured by Canon Inc.) shown in FIG. 9.Here, the image forming apparatus had a developing device shown in FIG.5 and was equipped with a corona charging unit and a corona transferunit. A durability evaluation test of the developer carrier wasperformed for printing 800,000 sheets while supplying one-componentdeveloper. The one-component developer used was one containing thefollowing components.

[0359] 100 parts of styrene-acrylic resin;

[0360] 95 parts of magnetite;

[0361] 2 parts of aluminum complex of di-tertiary butyl salicylic acid;and

[0362] 4 parts of low-molecular weight polypropylene.

[0363] The above materials were mixed by a Henschel mixer and themixture was then dissolved, kneaded, and dispersed using a biaxialextruder. The kneaded product was cooled and was then roughly pulverizedwith a hammer mill. Furthermore, the roughly pulverized product waspulverized into fine powders using a mechanical powdering machine,followed by being subjected to classification using an airflowclassifier to obtain fine powders (toner particles) having anumber-average particle size of 6.3 μm. Subsequently, 1.2 parts ofhydrophobic colloidal silica treated with a silane coupling agent and 3parts of strontium titanate were externally added to 100 parts of thefine powders to obtain magnetic toner. The resulting magnetic toner wasprovided as the one-component developer.

[0364] (Evaluation)

[0365] A durability test was performed with respect to the followingevaluation items for evaluating each of the developer carriers of theexamples and the comparative examples.

[0366] An evaluation test was performed by the same method as that ofExample 1-8 for evaluating image qualities with respect to imagedensity, fogging, sleeve ghost, blotch, uniformity of half-tone, and soon; the amount of charge on toner on the developer carrier (Q/M); thetransfer amount of toner (M/S); the abrasion resistance of the resincoating layer; and the stain resistance of the resin coating layer ofthe developer carrier. In each of evaluating items, the durabilityevaluations were performed under the surroundings of normal-temperatureand normal-humidity (N/N, 20° C./60%), normal-temperature andlow-humidity (N/L, 24° C./10%), and high-temperature and high-humidity(H/H, 32° C./80%), respectively. The results are listed in Tables 1-7and 1-8. As shown in the tables, good results were obtained for both theimage qualities and durability. TABLE 1 7 Results of evaluating thedurability on IR8500 (with respect to image density, fogging, sleeveghost, blotch, and uniformity of half-tone image) Uniformity ofhalf-tone Image density Fogging Sleeve ghost Blotch image 800,000800,000 800,000 800,000 800,000 Environment Initial sheets Initialsheets Initial sheets Initial sheets Initial sheets Example N/N 1.511.52 1.3 1.5 A A A A A A 1-10 H/H 1.48 1.46 0.9 1.2 A A A A A A N/L 1.521.50 1.5 1.8 A B A A A A Example N/N 1.50 1.52 1.2 1.6 A A A A A A 1-11H/H 1.44 1.41 0.8 1.4 A A A A A B N/L 1.51 1.51 1.3 1.8 A A A A A AExample N/N 1.53 1.52 1.4 2.0 A B A A A A 1-12 H/H 1.49 1.46 0.9 1.6 A BA A A B N/L 1.53 1.46 1.7 2.4 A C A B A C Example N/N 1.52 1.51 1.4 1.7A A A A A B 1-13 H/H 1.47 1.44 0.9 1.3 A A A A A C N/L 1.53 1.50 1.6 2.0A B A B A C Comparative N/N 1.37 0.98 1.7 3.0 B D A D A D Example 1-7H/H 1.30 0.92 1.4 3.2 A C A D C F N/L 1.40 0.99 3.5 4.1 B E A E B FComparative N/N 1.44 0.85 2.6 4.5 D F D F B F Example 1-8 H/H 1.42 0.861.6 4.1 C F C F C G N/L 1.30 0.80 3.7 5.2 E F D F B G Comparative N/N1.46 0.94 1.9 3.2 B D B D B D Example 1-9 H/H 1.44 0.92 1.6 3.1 B C A DC E N/L 1.34 0.87 3.1 4.2 C E C E B E

[0367] TABLE 1 8 Results of evaluating the durability on Ir8500 (withrespect to Q/M, M/S, abrasion resistance, and stain resistance) abrasionresistance Q/M(mC/Kg) M/S(dg/m²) After Amount of 800,000 800,000 Initialdurability chipping Stain Environment Initial sheets Initial sheets Ra(μm) Ra (μm) (μm) resistance Example N/N 16.7 15.7 1.11 1.13 0.98 0.952.0 A 1-10 H/H 15.4 14.5 1.07 1.02 0.98 0.94 2.4 A N/L 17.7 17.2 1.151.18 0.98 0.97 1.7 A Example N/N 15.0 14.0 1.09 1.06 0.95 0.90 2.6 A1-11 H/H 13.7 12.7 1.01 0.97 0.95 0.87 3.0 B N/L 15.8 15.0 1.12 1.100.95 0.92 2.3 A Example N/N 16.5 15.2 1.13 1.10 1.00 0.98 1.8 A 1-12 H/H15.8 13.5 1.09 0.96 1.00 0.97 2.2 B N/L 17.9 14.2 1.17 1.11 1.00 0.991.4 B Example N/N 16.6 15.3 1.02 0.97 0.78 0.73 2.7 A 1-13 H/H 15.7 14.30.98 0.93 0.78 0.71 3.1 B N/L 17.6 16.2 1.04 0.99 0.78 0.75 2.4 BComparative N/N 11.6 5.7 1.12 0.68 1.00 0.64 9.6 C Example 1-7 H/H 8.84.3 1.08 0.76 1.00 0.57 10.1 D N/L 12.6 6.2 1.20 0.71 1.00 0.69 8.0 DComparative N/N 14.7 6.7 1.11 0.90 0.95 0.93 1.3 C Example 1-8 H/H 13.76.4 1.02 0.86 0.95 0.91 1.8 D N/L 13.2 5.7 1.22 0.78 0.95 0.88 1.1 DComparative N/N 16.5 8.6 1.21 0.93 1.01 0.98 1.6 C Example 1-9 H/H 14.57.6 1.15 0.86 1.01 0.95 2.1 C N/L 14.8 7.1 1.23 0.93 1.01 0.96 1.4 D

EXAMPLE 1-11 TO EXAMPLE 1-13

[0368] Developer carriers B-1-11 to B-1-13 are obtained by the samemanufacturing method as that of Example 1-10 except that the graphitizedparticles A-1-2 to A-1-4 are respectively used as graphitized particlesof the resin coating layer instead of A-1-1. The same evaluation test asExample 1-10 was performed with the developer carrier B-1-11 to B-1-13.The formulation and the physical properties of the resin coating layerof the resulting developer carrier are listed in Table 1-2. The resultsof the evaluation tests are listed in Tables 1-7 and 1-8.

Comparative Example 1-7 to Comparative Example 1-9

[0369] Developer carriers C-1-7 to C-1-9 are obtained by the samemanufacturing method as that of Example 1-10 except that the graphitizedparticles a-1-1 to 1-1-3 are respectively used as graphitized particlesof the resin coating layer instead of A-1-1. The same evaluation test asExample 1-10 was performed with the developer carrier C-1-7 to C-1-9.The formulation and the physical properties of the resin coating layerof the resulting developer carrier are listed in Table 1-2. The resultsof the evaluation tests are listed in Tables 1-7 and 1-8.

EXAMPLE 2-1

[0370] As a raw material of graphitized particles, β-resin was extractedfrom coal tar pitch using a solvent fractionation. Then, the β-resin wasmade heavier with hydrogenation, followed by removing the solventsoluble fraction with toluene to obtain bulk meso-phase pitch. Theresulting bulk meso-phase pitch was pulverized and was then oxidized atabout 300° C. in the air, followed by primary baking at 1,200° C. undernitrogen atmosphere for carbonization. Subsequently, the carbonizedproduct was subjected to a secondary baking at 3,000° C. under nitrogenatmosphere for graphitization, followed by classification. Consequently,graphitized particles A-2-1 having a number-average particle size of 5.6μm were obtained. The physical properties of the graphitized particlesare listed in Table 2-1.

[0371] 200 parts of resol-type phenol resin solution (containing 50%methanol);

[0372] 40 parts of graphitized particles (A-2-1);

[0373] 4 parts of conductive carbon black; and

[0374] 120 parts of methanol.

[0375] Glass beads of 1 mm in diameter were added as media particles ina mixture of the above materials and were then dispersed by a sand mill.Subsequently, the solid fraction in the resulting dispersion solutionwas diluted to 35% with methanol to obtain a coating solution.

[0376] Using the coating solution and a spray method, a resin coatingfilm was formed on an aluminum cylindrical tube having an outer diameterof 32 mmφ and an arithmetic mean roughness Ra of 0.2 μm prepared bygrinding. After that, the resin coating film was dried and hardened byheating in a direct drying furnace at 150° C. for 30 minutes to obtain adeveloper carrier B-2-1. The formulation and the physical properties ofthe resulting developer carrier B-2-1 are listed in Table 2-2.

[0377] The developer carrier B-2-1 was mounted on an image formingapparatus (Model: NP6085, manufactured by Canon Inc.) shown in FIG. 9.Here, the image forming apparatus had a developing device shown in FIG.5 and was equipped with a corona charging unit and a corona transferunit. A durability evaluation test of the developer carrier wasperformed for printing 800,000 sheets while supplying one-componentdeveloper. The one-component developer used was one containing thefollowing components.

[0378] 100 parts of polyester resin;

[0379] 95 parts of magnetite;

[0380] 2 parts of aluminum complex of di-tertiary butyl salicylic acid;and

[0381] 4 parts of low-molecular weight polypropylene.

[0382] The above materials were kneaded, pulverized, and classified by atypical dry toner method to obtain fine powders (toner particles) havingthe number-average particle size of 6.1 μm. Subsequently, 1.2 parts ofhydrophobic colloidal silica treated with a silane coupling agent and 3parts of strontium titanate were externally added to 100 parts of thefine powders to obtain magnetic toner. The resulting magnetic toner wasprovided as the one-component developer.

[0383] (Evaluation) A durability test was performed with respect to thefollowing evaluation items for evaluating each of the developer carriersof the examples and the comparative examples.

[0384] An evaluation test was performed for evaluating image qualitieswith respect to image density, fogging, sleeve ghost, blotch, uniformityof half-tone image, and so on; the amount of charge on toner on thedeveloper carrier (Q/M); the transfer amount of toner (M/S); and theabrasion resistance of the resin coating layer. Each of the evaluationtest were conducted under the surroundings of normal-temperature andnormal-humidity (N/N, 20° C./60%), normal-temperature and low-humidity(N/L, 24° C./10%), and high-temperature and high-humidity (H/H, 30°C./80%), respectively.

[0385] The results are listed in Tables 2-3 and 2-4. As shown in thetables, good results were obtained for both the image qualities anddurability.

[0386] (2-1) Image Density

[0387] Using a reflection densitometer RD918 (manufactured by Macbeth),the density of black solid image portion obtained by solid printing wasmeasured with respect to each of five different points on the image. Theaverage of the total measurement results was defined as the imagedensity.

[0388] (2-2) Fogging Density

[0389] The reflectivity (D1) of a white solid portion of the imageformed on a sheet of recording paper was measured. Furthermore, thereflectivity (D2) of a blank of another sheet of the same recordingpaper was measured. Then, the difference between D1 and D2 (i.e., thevalue of D1−D2) was obtained with respect to each of five differentpoints. The average of the total measurement results was defined as thefogging density. The reflectivity was measured using TC-6DS(manufactured by Tokyo Denshoku).

[0390] (2-3) Sleeve Ghost

[0391] The position of developing sleeve obtained by developing animage, in which a white solid portion and a black solid portion wereadjacent to each other, was placed on a developing position at the timeof a subsequent turn of the developing sleeve so as to develop ahalf-tone image. Then, the difference in gradation emerged on thehalf-tone image was visually observed and was then evaluated on thebasis of the following criteria.

[0392] A: No difference in gradation was observed.

[0393] B: A slight difference in gradation was observed

[0394] C: A small difference in gradation was observed but practicallyallowable.

[0395] D: Practically controversial difference in gradation was observedover one lap of sleeve.

[0396] E: Practically controversial difference in gradation was observedover two laps of sleeve.

[0397] (2-4) Blotch (Image Defect)

[0398] Various kinds of images such as black solid, half-tone, and lineimages were formed. Image defects such as wave-like unevenness andblotch (dot-like unevenness), and defective toner coating on thedeveloping sleeve at the time of image formation were visually observedand the results of the observations were referenced to evaluate on thebasis of the following criteria.

[0399] A: Any defect could not be observed on the image and the sleeve.

[0400] B: A defect was slightly found on the sleeve, but substantiallyno defect was observed on the image.

[0401] C: A defect was observed on a half-tone image or black solidimage in the first sheet of the recording paper and also observed on thesleeve at first rotation of the sleeve cycle.

[0402] D: A defect was observed on the half-tone image or black solidimage, but practically allowable.

[0403] E: A practically controversial image defect was observed on thewhole black solid image.

[0404] F: A practically controversial image defect was not only observedon the black solid image but also observed on the white solid image.

[0405] (2-5) Uniformity of Half-Tone Image (Generation of White Streakor White Belt)

[0406] The resulting image was visually observed with respect to linearor belt-shaped streak extending in the direction of image formation tobe generated particularly in a half-tone image, followed by evaluatingon the basis of the following criteria.

[0407] A: Any defect was found in both the image and the sleeve at all.

[0408] B: A defect was slightly observed when the image was carefullyobserved, but it was hardly recognized at a glance.

[0409] C: A defect was slightly observed in the half-tone image, whileit was substantially no problem in the black solid image.

[0410] D: A streak was observed in the half-tone image, while it wasslightly observed in the black solid image.

[0411] E: The difference in gradation was also observed in the blacksolid image, but practically allowable.

[0412] F: A practically controversial difference in gradation wasobserved in the whole black solid image.

[0413] G: Low image density and the images having many streaks weredistinctly observed.

[0414] (2-6) The Amount of Charge on Toner (Q/M) and the Transfer Amountof Toner (M/S)

[0415] Toner carried on the developing sleeve was absorbed and collectedinto a cylindrical metal tube and a cylindrical filter. At this time,the amount of charge per unit mass Q/M (mC/kg) and the mass of toner perunit area M/S(dg/m²) were calculated from the amount of electrostaticcharge Q accumulated in a capacitor through the cylindrical metal tube,the mass M of the collected toner, and the area S from which the tonerwas absorbed, to be defined as the amount of charge on toner (Q/M) andthe transfer amount of toner (M/S), respectively.

[0416] (2-7) Abrasion Resistance of Resin Coating Layer

[0417] The arithmetic mean roughness (Ra) of the developer carriersurface before and after the durability test and the amount of chippingin the film thickness of the resin coating layer were measured.

EXAMPLE 2-2 AND EXAMPLE 2-3

[0418] Graphitized particles A-2-2 and A-2-3 were obtained by the samemanufacturing method as that of the graphitized particles A-2-1 exceptthat the temperature of secondary baking was changed as shown in Table2-1 from one used in Example 2-1. The physical properties of thegraphitized particles A-2-2 and A-2-3 are listed in Table 2-1. Developercarriers B-2-2 and B-2-3 were obtained by the same manufacturing methodas that of Example 2-1 except that the graphitized particles A-2-2 andA-2-3 are used as graphitized particles of the resin coating layerinstead of A-2-1. The same evaluation test as Example 2-1 was performedwith the developer carriers B-2-2 and B-2-3. The formulation and thephysical properties of the resin coating layer of the resultingdeveloper carrier are listed in Table 2-2. The results of the evaluationtests are listed in Tables 2-3 and 2-4.

EXAMPLE 2-4

[0419] Graphitized particles A-2-4 having the number-average particlesize of 2.5 μm were obtained by the same manufacturing method as that ofthe graphitized particles A-2-1 except that the pulverization conditionsfor bulk mesophase pitch and the classification conditions after thesecond baking of the raw material used in Example 2-1 were changed. Thephysical properties of the graphitized particles A-2-4 are listed inTable 2-1. Developer carrier B-2-4 is obtained by the same manufacturingmethod as that of Example 2-1 except that the graphitized particlesA-2-4 are used as graphitized particles of the resin coating layerinstead of A-2-1. The same evaluation test as Example 2-1 was performedwith the developer carrier B-2-4. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 2-2. The results of the evaluation tests are listedin Tables 2-3 and 2-4.

EXAMPLE 2-5

[0420] As a raw material of graphitized particles, coal heavy oil washeated to obtain crude mesocarbon micro beads. The resulting crudemesocarbon micro beads were subjected to centrifugal separation,followed by washing and purifying with benzene and drying. Subsequently,the dried product was mechanically dispersed using an atomizer mill toobtain the meso-carbon micro beads. The meso-carbon micro beads weresubjected to a primary baking at 1,200° C. under nitrogen atmosphere forcarbonization, followed by being subjected to a second dispersion withthe atomizer mill. The resulting dispersed product was subjected to asecond baking at 2,800° C. under nitrogen atmosphere for graphitization,and was then classified. Consequently, graphitized particles A-2-5having a number-average particle size of 6.1 μm were obtained. Thephysical properties of the graphitized particles A-2-5 are listed inTable 2-1.

[0421] Developer carrier B-2-5 is obtained by the same manufacturingmethod as that of Example 2-1 except that the graphitized particlesA-2-5 are used as graphitized particles of the resin coating layerinstead of A-2-1. The same evaluation test as Example 2-1 was performedwith the developer carrier B-2-5. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 2-2. The results of the evaluation tests are listedin Tables 2-3 and 2-4.

EXAMPLE 2-6 AND EXAMPLE 2-7

[0422] Graphitized particles A-2-6 and A-2-7 were obtained by the samemanufacturing method as that of graphitized particles A-2-5 except thatthe temperature of the secondary baking for obtaining the graphitizedparticles in Example 2-5 was changed. The physical properties of thegraphitized particles A-2-6 and A-2-7 are listed in Table 2-1.

[0423] Developer carriers B-2-6 and B-2-7 are obtained by the samemanufacturing method as that of Example 2-1 except that the graphitizedparticles A-2-6 and A-2-7 are used as graphitized particles of the resincoating layer instead of A-2-1. The same evaluation test as Example 2-1was performed with the developer carriers B-2-6 and B-2-7. Theformulation and the physical properties of the resin coating layer ofthe resulting developer carrier are listed in Table 2-2. The results ofthe evaluation tests are listed in Tables 2-3 and 2-4.

Comparative Example 2-1

[0424] As raw materials of graphitized particles, a mixture of coke andtar pitch was used. The mixture was kneaded at a temperature of over thesoftening point of the tar pitch and was then extruded by extrusion,followed by being subjected to a primary baking at 1,000° C. undernitrogen atmosphere for carbonization. In the resulting carbide, coaltar pitch was immersed. Then, the immersed product was graphitized by asecondary baking at 2,800° C. under nitrogen atmosphere. Subsequently,the mixture was pulverized and classified. Consequently, graphitizedparticles a-2-1 having a number-average particle size of 6.1 μm wereobtained. The physical properties of the graphitized particles a-2-1 arelisted in Table 2-1.

[0425] Developer carrier C-2-1 are obtained by the same manufacturingmethod as that of Example 2-1 except that the graphitized particlesa-2-1 are used as graphitized particles of the resin coating layerinstead of A-2-1. The same evaluation test as Example 2-1 was performedwith the developer carriers C-2-1. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 2-2. The results of the evaluation tests are listedin Tables 2-3 and 2-4.

Comparative Example 2-2

[0426] As a raw material of graphitized particles, spherical phenolresin particles were used. The particles were baked at 2,200° C. undernitrogen atmosphere, followed by classification. Consequently,graphitized particles a-2-2 having a number-average particle size of 5.7μm were obtained. The physical properties of the graphitized particlesa-2-2 are listed in Table 2-1.

[0427] Developer carrier C-2-2 are obtained by the same manufacturingmethod as that of Example 2-1 except that the graphitized particlesa-2-2 are used as graphitized particles of the resin coating layerinstead of A-2-1. The same evaluation test as Example 2-1 was performedwith the developer carriers C-2-2. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 2-2. The results of the evaluation tests are listedin Tables 2-3 and 2-4.

Comparative Example 2-3

[0428] Graphitized particles a-2-3 were obtained by the samemanufacturing method as that of the graphitized particles A-2-1 exceptthat the temperature of the secondary baking for obtaining thegraphitized particles in Example 2-1 was changed. The physicalproperties of the graphitized particles a-2-3 are listed in Table 2-1.Developer carrier C-2-3 is obtained by the same manufacturing method asthat of Example 2-1 except that the graphitized particles a-2-3 are usedas graphitized particles of the resin coating layer instead of A-2-1.The same evaluation test as Example 2-1 was performed with the developercarriers C-2-3. The formulation and the physical properties of the resincoating layer of the resulting developer carrier are listed in Table2-2. The results of the evaluation tests are listed in Tables 2-3 and2-4.

Comparative Example 2-4 and Comparative Example 2-5

[0429] Graphitized particles a-2-4 and a-2-5 were obtained by the samemanufacturing method as that of the graphitized particles A-2-5 exceptthat the temperature of the secondary baking for obtaining thegraphitized particles in Example 2-5 was changed. The physicalproperties of the graphitized particles a-2-4 and a-2-5 are listed inTable 2-1. Developer carriers C-2-4 and C-2-5 are obtained by the samemanufacturing method as that of Example 2-1 except that the graphitizedparticles a-2-4 and a-2-5 are used as graphitized particles of the resincoating layer instead of A-2-1. The same evaluation test as Example 2-1was performed with the developer carriers C-2-4 and C-2-5. Theformulation and the physical properties of the resin coating layer ofthe resulting developer carrier are listed in Table 2-2. The results ofthe evaluation tests are listed in Tables 2-3 and 2-4. TABLE 2 1Physical properties of particles added in resin coating layer ParticleBaking Number-average Lattice spacing Degree of Average degree of typeRaw material temperature particle size (μm) d (002) (Å) graphitization p(002) circularity SF-1 A-2-1 Bulk mesophase 3000 5.6 3.3658 0.37 0.68pitch particles A-2-2 Bulk mesophase 3200 5.3 3.3598 0.26 0.68 pitchparticles A-2-3 Bulk mesophase 2200 5.8 3.4090 0.80 0.69 pitch particlesA-2-4 Bulk mesophase 3000 2.5 3.3671 0.39 0.67 pitch particles A-2-5Meso-carbon micro 2800 6.1 3.3603 0.27 0.72 beads A-2-6 Meso-carbonmicro 3100 5.9 3.3585 0.23 0.71 beads A-2-7 Meso-carbon micro 2200 6.43.4063 0.78 0.73 beads A-2-8 Bulk mesophase 3000 10.3 3.3607 0.28 0.70pitch particles A-2-9 Bulk mesophase 2300 10.5 3.3998 0.73 0.68 pitchparticles A-2-10 Bulk mesophase 3000 19.7 3.3603 0.27 0.71 pitchparticles a-2-1 Coke and tar pitch 2800 6.1 3.3550 0.11 0.60 a-2-2Phenol resin 2200 5.7 Incapable Incapable measurement 0.86 particlesmeasurement a-2-3 Bulk mesophase 1800 5.8 3.4488 1.05 0.69 pitchparticles a-2-4 Meso-carbon micro 1800 6.5 3.4417 1.01 0.73 beads a-2-5Meso-carbon micro 3500 6.0 3.3562 0.16 0.70 beads a-2-6 Coke and tarpitch 2800 11.5 3.3547 0.09 0.58 a-2-7 Bulk mesophase 1800 10.6 3.44171.01 0.69 pitch particles a-2-8 Phenol resin 2200 10.9 IncapableIncapable measurement 0.87 particles measurement a-2-9 Coke and tarpitch 2800 20.2 3.3547 0.09 0.59

[0430] TABLE 2 2 Formulation and physical properties of resin coatinglayer of developer carrier Structure of resin coating layer OtherExamples and Graphitized spherical Conductive fine Film VolumeComparative Developer particles particles particles Coating resinthickness Ra resistivity Examples carrier (parts) (parts) (parts)(parts) (μm) (μm) (Ω · cm) Example 2-1 B-2-1 A-2-1 (40) — Carbon black(4) Phenol resin (100) 15.3 0.94 1.38 Example 2-2 B-2-2 A-2-2 (40) —Carbon black (4) Phenol resin (100) 15.8 0.91 1.04 Example 2-3 B-2-3A-2-3 (40) — Carbon black (4) Phenol resin (100) 15.2 0.95 3.98 Example2-4 B-2-4 A-2-4 (40) — Carbon black (4) Phenol resin (100) 15.0 0.711.40 Example 2-5 B-2-5 A-2-5 (40) — Carbon black (4) Phenol resin (100)15.2 1.01 1.05 Example 2-6 B-2-6 A-2-6 (40) — Carbon black (4) Phenolresin (100) 15.3 0.97 0.98 Example 2-7 B-2-7 A-2-7 (40) — Carbon black(4) Phenol resin (100) 15.7 1.00 3.64 Example 2-8 B-2-8 A-2-8 (45) —Carbon black (5) Urethane resin 16.3 1.62 0.97 (100) Example 2-9 B-2-9A-2-9 (45) — Carbon black (5) Urethane resin 18.5 1.85 3.11 (100)Example 2-10 B-2-10 A-2-10 (30) — Carbon black (15) Urethane resin 20.12.30 0.68 (100) Example 2-11 B-2-11 A-2-1 (45) a-2-8 (12) Carbon black(5) Phenol resin (100) 15.6 2.03 1.19 Example 2-12 B-2-12 A-2-2 (45)a-2-8 (12) Carbon black (5) Phenol resin (100) 15.9 1.98 1.08 Example2-13 B-2-13 A-2-3 (45) a-2-8 (12) Carbon black (5) Phenol resin (100)16.2 2.01 1.33 Example 2-14 B-2-14 A-2-6 (45) a-2-8 (12) Carbon black(5) Phenol resin (100) 18.1 2.13 1.12 Example 2-15 B-2-15 A-2-1 (30)a-2-2 (9) Carbon black MMA-DM resin (100) 13.7 0.82 16.3 (3.5) Example2-16 B-2-16 A-2-2 (30) a-2-2 (9) Carbon black MMA-DM resin (100) 13.50.79 11.2 (3.5) Example 2-17 B-2-17 A-2-3 (30) a-2-2 (9) Carbon blackMMA-DM resin (100) 13.8 0.83 19.6 (3.5) Comparative C-2-1 a-2-1 (40) —Carbon black (5) Phenol resin (100) 15.7 0.79 0.87 Example 2-1Comparative C-2-2 a-2-2 ((0) — Carbon black (5) Phenol resin (100) 15.90.99 50.3 Example 2-2 Comparative C-2-3 a-2-3 (40) — Carbon black (5)Phenol resin (100) 15.4 098 35.8 Example 2-3 Comparative C-2-4 a-2-4(40) — Carbon black (5) Phenol resin (100) 15.5 0.95 0.95 Example 2-4Comparative C-2-5 a-2-5 (40) — Carbon black (5) Phenol resin (100) 15.90.88 0.91 Example 2-5 Comparative C-2-6 a-2-6 (45) — Carbon black (5)Urethane resin 16.5 1.51 0.75 Example 2-6 (100) Comparative C-2-7 a-2-7(45) — Carbon black (5) Urethane resin 16.4 1.57 9.87 Example 2-7 (100)Comparative C-2-8 a-2-8 (45) — Carbon black (5) Urethane resin 16.2 1.8215.8 Example 2-8 (100) Comparative C-2-9 a-2-9 (30) — Carbon black (15)Urethane resin 20.2 2.02 0.66 Example 2-9 (100) Comparative C-2-10 a-2-1(45) a-2-8 (12) Carbon black (5) Phenol resin (100) 15.3 1.95 1.36Example 2-10 Comparative C-2-11 a-2-2 (45) a-2-8 (12) Carbon black (5)Phenol resin (100) 15.8 2.06 48.6 Example 2-11 Comparative C-2-12 a-2-3(45) a-2-8 (12) Carbon black (5) Phenol resin (100) 15.6 2.04 29.7Example 2-12 Comparative C-2-13 a-2-1 (30) a-2-2 (9) Carbon black MMA-DMresin (100) 13.2 0.82 16.1 Example 2-13 (3.5) Comparative C-2-14 a-2-2(30) a-2-2 (9) Carbon black MMA-DM resin (100) 13.9 0.93 285.0 Example2-14 (3.5) Comparative C-2-15 a-2-3 (30) a-2-2 (9) Carbon black MMA-DMresin (100) 13.3 0.87 180.0 Example 2-15 (3.5)

[0431] TABLE 2 3 Results of evaluating the durability on NP6085 (withrespect to image density, fogging, sleeve ghost, blotch, and uniformityof half-tone image) Uniformity of half- En- Image density Fogging Sleeveghost Blotch tone image viron- 400,000 800,000 400,000 800,000 400,000800,000 400,000 800,000 400,000 800,000 ment Initial sheets sheetsInitial sheets sheets Initial sheets sheets Initial sheets sheetsInitial sheets sheets Ex- N/N 1.52 1.53 1.53 1.1 0.9 1.0 A A A A A A A AA am- H/H 1.48 1.47 1.46 0.7 0.7 0.8 A A A A A A A A B ple N/L 1.52 1.531.52 1.3 1.2 1.2 A A B A A A A A A 2-1 Ex- N/N 1.50 1.52 1.50 1.2 1.11.6 A A A A A A A A B am- H/H 1.45 1.44 1.42 0.8 0.8 1.0 A A A A A A A BB ple N/L 1.53 1.53 1.50 1.6 1.5 1.9 A A B A A A A A A 2-2 Ex- N/N 1.531.54 1.54 1.2 1.4 1.6 A A B A A A A A A am- H/H 1.49 1.48 1.47 0.8 1.01.3 A A B A A A A B B ple N/L 1.53 1.50 1.48 1.5 1.6 1.8 A B C A A B A AB 2-3 Ex- N/N 1.52 1.52 1.51 1.0 1.0 1.2 A A A A A A A B B am- H/H 1.481.46 1.45 0.7 0.8 0.9 A A A A A A A C D ple N/L 1.52 1.52 1.51 1.3 1.31.4 A A B A A A A B C 2-4 Ex- N/N 1.52 1.53 1.52 1.2 1.0 1.1 A A A A A AA A A am- H/H 1.48 1.48 1.46 0.8 0.8 0.9 A A A A A A A A B ple N/L 1.531.53 1.52 1.4 1.2 1.3 A A A A A A A A A 2-5 Ex- N/N 1.50 1.51 1.49 1.11.2 1.6 A A A A A A A A B am- H/H 1.44 1.43 1.41 0.8 0.9 1.0 A A A A A AA B B ple N/L 1.53 1.52 1.51 1.5 1.6 1.8 A A B A A A A A A 2-6 Ex- N/N1.54 1.52 1.50 1.3 1.5 1.6 A A B A A A A A A am- H/H 1.49 1.49 1.47 0.91.0 1.3 A A B A A A A B B ple N/L 1.52 1.50 1.48 1.4 1.8 1.7 A B C A A BA A B 2-7 Com- N/N 1.35 1.10 0.96 1.6 1.7 2.8 B C D A C D B D F para-H/H 1.28 1.06 0.90 1.3 2.4 3.1 A C D A D E C E G tive N/L 1.39 1.16 1.023.5 3.3 4.0 B D E A E F B F G Ex- am- ple 2-1 Com- N/N 1.43 1.09 0.872.5 3.4 4.3 D E F D E F B E F para- H/H 1.41 0.99 0.83 1.5 3.0 4.0 C E FC E F C E G tive N/L 1.32 1.06 0.82 3.7 4.6 5.3 E F F D E F B F G Ex-am- ple 2-2 Com- N/N 1.45 1.15 0.96 1.8 3.0 2.9 B C C B C D B C D para-H/H 1.42 1.09 0.93 1.4 2.6 3.1 B C C A C D C D E tive N/L 1.36 1.10 0.892.9 3.4 4.0 C D E C D E B C E Ex- am- ple 2-3 Com- N/N 1.46 1.16 0.981.7 2.8 2.8 B C C B C D B C D para- H/H 1.43 1.09 0.95 1.3 2.5 3.0 B C CA C D C D E tive N/L 1.37 1.13 0.92 2.8 3.2 3.7 C D E C D E B C E Ex-am- ple 2-4 Com- N/N 1.45 1.30 1.20 1.5 2.1 2.5 A B C A A B A B C para-H/H 1.36 1.18 1.10 1.6 2.8 3.1 A C D A A B B C D tive N/L 1.46 1.32 1.172.9 3.3 3.6 A C D A B C A B C Ex- am- ple 2-5

[0432] TABLE 2 4 Results of evaluating the durability on NP6085 (withrespect to Q/M, M/S, and abrasion resistance) Q/M(mC/Kg) M/S(dg/m²)Abrasion resistance 400,000 800,000 400,000 800,000 Initial Afterdurability Ra Amount of chipping Environment Initial sheets sheetsInitial sheets sheets Ra(μm) (μm) (μm) Example 2-1 N/N 15.4 16.1 15.81.08 1.09 1.08 0.94 0.92 2.3 H/H 15.5 15.0 14.6 1.05 1.03 1.01 0.94 0.902.7 N/L 17.6 17.5 17.3 1.11 1.13 1.14 0.94 0.93 1.9 Example 2-2 N/N 14.914.7 14.1 1.05 1.04 1.02 0.91 0.86 2.6 H/H 13.8 13.4 12.7 1.00 0.97 0.940.91 0.83 3.2 N/L 15.7 15.5 15.1 1.07 1.08 1.04 0.91 0.88 2.3 Example2-3 N/N 16.6 18.2 15.3 1.09 1.10 1.04 0.95 0.93 1.9 H/H 15.7 14.7 13.61.06 1.00 0.95 0.95 0.92 2.3 N/L 17.8 15.7 14.4 1.13 1.16 1.08 0.95 0.941.6 Example 2-4 N/N 16.8 15.9 154 1.05 1.03 0.99 0.71 0.66 2.8 H/H 16.015.1 14.5 1.01 0.95 0.92 0.71 0.64 3.3 N/L 17.7 16.8 16.3 1.08 1.07 1.030.71 0.68 2.5 Example 2-5 N/N 16.5 16.1 15.9 1.10 1.11 1.10 1.01 0.982.2 H/H 15.7 15.2 14.9 1.07 1.05 1.04 1.01 0.95 2.6 N/L 17.5 17.4 17.31.12 1.13 1.11 1.01 0.99 1.8 Example 2-6 N/N 15.0 14.8 14.1 1.08 1.071.04 0.97 0.92 2.5 H/H 14.0 13.4 13.1 1.04 1.00 0.97 0.97 0.88 3.2 N/L15.6 15.6 15.2 1.10 1.12 1.08 0.97 0.90 2.2 Example 2-7 N/N 16.7 16.015.2 1.13 1.14 1.16 1.00 0.94 1.8 H/H 15.9 14.6 13.6 1.08 1.01 0.95 1.000.97 2.3 N/L 17.8 16.7 16.0 1.15 1.17 1.10 1.00 0.98 1.7 Comparative N/N11.9 8.8 5.9 1.05 0.83 0.65 0.79 0.42 9.9 Example 2-1 H/H 9.2 6.8 4.50.98 0.75 0.62 0.79 0.36 10.7 N/L 12.9 9.2 6.3 1.10 0.86 0.67 0.79 0.478.9 Comparative N/N 14.5 8.6 6.5 1.18 1.02 0.88 0.99 0.95 1.5 Example2-2 H/H 13.6 8.9 6.0 1.11 0.97 0.81 0.99 0.92 2 N/L 13.0 9.0 5.8 1.210.95 0.77 0.99 0.89 1.3 Comparative N/N 16.3 10.9 8.8 1.19 1.06 0.920.98 0.97 1.7 Example 2-3 H/H 14.3 10.5 7.3 1.13 0.99 0.85 0.98 0.93 2.2N/L 14.6 10.3 7.1 1.22 1.03 0.63 0.98 0.91 1.6 Comparative N/N 16.1 11.18.9 1.17 1.04 0.90 0.95 0.94 1.6 Example 2-4 H/H 14.4 10.4 7.1 1.12 1.000.87 0.95 0.90 2.1 N/L 14.9 10.4 7.2 1.21 1.05 0.84 0.95 0.89 1.7Comparative N/N 12.9 11.4 10.0 1.15 1.02 0.91 0.88 0.62 4.1 Example 2-5H/H 10.7 9.8 8.7 1.10 0.97 0.86 0.88 0.53 5.3 N/L 13.9 11.9 9.8 1.171.04 0.93 0.88 0.66 3.6

EXAMPLE 2-8

[0433] Graphitized particles A-2-8 having the number-average particlesize of 10.3 μm were obtained by the same manufacturing method as thatof the graphitized particles A-2-1 except that the pulverizationconditions for bulk mesophase pitch and the classification conditionsafter the second baking of the raw material used in Example 2-1 werechanged. The physical properties of the graphitized particles A-2-8 arelisted in Table 2-1.

[0434] 200 parts of urethane resin solution (containing 50% toluene);

[0435] 45 parts of graphitized particles (A-2-8);

[0436] 5 parts of conductive carbon black; and

[0437] 160 parts of toluene.

[0438] Glass beads of 1 mm in diameter were added as media particles ina mixture of the above materials and were then dispersed by a sand mill.Subsequently, the solid fraction in the resulting dispersion solutionwas diluted to 27% with methanol to obtain a coating solution.

[0439] Using the coating solution and a spray method, a resin coatingfilm was formed on, an aluminum cylindrical tube having an outerdiameter of 16 mmφ and an arithmetic mean roughness Ra of 0.3 μmprepared by grinding. After that, the resin coating film was dried andhardened by heating in a direct drying furnace at 150° C. for 30 minutesto obtain a developer carrier B-2-8. The formulation and the physicalproperties of the resulting developer carrier B-2-8 are listed in Table2-2.

[0440] The developer carrier B-2-8 was mounted on an image formingapparatus (Model: LBP730, manufactured by Canon Inc.) shown in FIG. 7.Here, the image forming apparatus had a developing device shown in FIG.7 and was equipped with charging means for a contact roller andtransferring means for the contact roller. A durability evaluation testof the developer carrier was performed for printing 20,000 sheets whilesupplying one-component developer. The one-component developer used wasone containing the following components.

[0441] 100 parts of styrene-acrylic resin;

[0442] 95 parts of magnetite;

[0443] 1.5 parts of aluminum complex of di-tertiary butyl salicylicacid; and

[0444] 4.5 parts of low-molecular weight polypropylene.

[0445] The above materials were kneaded, pulverized, and classified by atypical dry toner method to obtain fine powders (toner particles) havingthe number-average particle size of 6.1 μm. Subsequently, 1.2 parts ofhydrophobic colloidal silica treated with a silane coupling agent wereexternally added to 100 parts of the fine powders to obtain magnetictoner. The resulting magnetic toner was provided as the one-componentdeveloper.

[0446] (Evaluation)

[0447] A durability test was performed with respect to the followingevaluation items for evaluating each of the developer carriers of theexamples and the comparative examples.

[0448] An evaluation test was performed by the same method as that ofExample 2-1 for evaluating image qualities with respect to imagedensity, fogging, sleeve ghost, blotch, uniformity of half-tone, and soon; the amount of charge on toner on the developer carrier (Q/M); thetransfer amount of toner (M/S); and the abrasion resistance of the resincoating layer. In each of evaluating items, the durability evaluationswere performed under the surroundings of normal-temperature andnormal-humidity (N/N, 20° C./60%), normal-temperature and low-humidity(N/L, 24° C./10%), and high-temperature and high-humidity (H/H, 32°C./80%), respectively. The results are listed in Tables 2-5 and 2-6. Asshown in the tables, good results were obtained for both the imagequalities and durability.

EXAMPLE 2-9

[0449] Graphitized particles A-2-9 were obtained by the samemanufacturing method as that of the graphitized particles A-2-8 exceptthat the temperature of secondary baking was changed as shown in Table2-1 from one used in Example 2-8. The physical properties of thegraphitized particles A-2-9 are listed in Table 2-1. Developer carrierB-2-9 was obtained by the same manufacturing method as that of Example2-8 except that the graphitized particles A-2-9 are used as graphitizedparticles of the resin coating layer instead of A-2-8. The sameevaluation test as Example 2-1 was performed with the developer carrierB-2-9. The formulation and the physical properties of the resin coatinglayer of the resulting developer carrier are listed in Table 2-2. Theresults of the evaluation tests are listed in Tables 2-5 and 2-6.

Comparative Example 2-6

[0450] As raw materials of graphitized particles, a mixture of coke andtar pitch was used. The mixture was kneaded at a temperature of over thesoftening point of the tar pitch and was then extruded by extrusion,followed by being subjected to a primary baking at 1,000° C. undernitrogen atmosphere for carbonization. In the resulting carbide, coaltar pitch was immersed. Then, the immersed product was graphitized by asecondary baking at 2,800° C. under nitrogen atmosphere. Subsequently,the mixture was pulverized and classified. Consequently, graphitizedparticles a-2-6 having a number-average particle size of 11.5 μm wereobtained. The physical properties of the graphitized particles a-2-6 arelisted in Table 2-1.

[0451] Developer carrier C-2-6 are obtained by the same manufacturingmethod as that of Example 2-8 except that the graphitized particlesa-2-6 are used as graphitized particles of the resin coating layerinstead of A-2-8. The same evaluation test as Example 1-8 was performedwith the developer carriers C-2-6. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 2-2. The results of the evaluation tests are listedin Tables 2-5 and 2-6.

Comparative Example 2-7

[0452] Graphitized particles a-2-7 were obtained by the samemanufacturing method as that of the graphitized particles A-2-8 exceptthat the temperature of secondary baking was changed as shown in Table2-1 from one used in Example 2-8. The physical properties of thegraphitized particles a-2-7 are listed in Table 2-1. Developer carrierC-2-7 was obtained by the same manufacturing method as that of Example2-8 except that the graphitized particles a-2-7 are used as graphitizedparticles of the resin coating layer instead of A-2-8. The sameevaluation test as Example 2-1 was performed with the developer carrierC-2-7. The formulation and the physical properties of the resin coatinglayer of the resulting developer carrier are listed in Table 2-2. Theresults of the evaluation tests are listed in Tables 2-5 and 2-6.

EXAMPLE 2-10

[0453] Graphitized particles A-2-10 having the number-average particlesize of 19.7 μm were obtained by the same manufacturing method as thatof the graphitized particles A-2-1 except that the pulverizationconditions for bulk mesophase pitch and the classification conditionsafter the second baking of the raw material used in Example 2-1 werechanged. The physical properties of the graphitized particles A-2-10 arelisted in Table 2-1.

[0454] 200 parts of an urethane resin solution (containing 50% toluene);

[0455] 30 parts of graphitized particles (A-2-10);

[0456] 15 parts of conductive carbon black; and

[0457] 120 parts of methanol.

[0458] Using the above materials, a coating solution was prepared by thesame method as that of Example 2-8 to prepare developer carrier B-2-10.Then, the same evaluation test as that of Example 2-8 was conducted. Theformulation and the physical properties of the resin coating layer ofthe developer carrier were shown in Table 2-2, and the evaluationresults were shown in Table 2-5 and Table 2-6, respectively.

Comparative Example 2-8

[0459] As a raw material of graphitized particles, spherical phenolresin particles were used. The particles were baked at 2,200° C. undernitrogen atmosphere, followed by classification. Consequently,graphitized particles a-2-8 having a number-average particle size of10.9 μm were obtained. The physical properties of the graphitizedparticles a-2-8 are listed in Table 2-1. Developer carrier C-2-8 areobtained by the same manufacturing method as that of Example 2-8 exceptthat the graphitized particles a-2-8 are used as graphitized particlesof the resin coating layer instead of A-2-8. The same evaluation test asExample 2-8 was performed with the developer carriers C-2-8. Theformulation and the physical properties of the resin coating layer ofthe resulting developer carrier are listed in Table 2-2. The results ofthe evaluation tests are listed in Tables 2-5 and 2-6.

Comparative Example 2-9

[0460] As raw materials of graphitized particles, a mixture of coke andtar pitch was used. The mixture was kneaded at a temperature of over thesoftening point of the tar pitch and was then extruded by extrusion,followed by being subjected to a primary baking at 1,000° C. undernitrogen atmosphere for carbonization. In the resulting carbide, coaltar pitch was immersed. Then, the immersed product was graphitized by asecondary baking at 2,800° C. under nitrogen atmosphere. Subsequently,the mixture was pulverized and classified. Consequently, graphitizedparticles a-2-9 having a number-average particle size of 20.2 μm wereobtained. The physical properties of the graphitized particles a-2-9 arelisted in Table 2-1.

[0461] Developer carrier C-2-9 are obtained by the same manufacturingmethod as that of Example 2-10 except that the graphitized particlesa-2-9 are used as graphitized particles of the resin coating layerinstead of A-2-10. The same evaluation test as Example 2-8 was performedwith the developer carriers C-2-9. The formulation and the physicalproperties of the resin coating layer of the resulting developer carrierare listed in Table 2-2. The results of the evaluation tests are listedin Tables 2-5 and 2-6. TABLE 2 5 Results of evaluating the durability onLBP730 (with respect to image density, fogging, sleeve ghost, blotch,and uniformity of half-tone image) Uniformity of half- En- Image densityFogging Sleeve ghost Blotch tone image viron- 10,000 20,000 10,00020,000 10,000 20,000 10,000 20,000 10,000 20,000 ment Initial sheetssheets Initial sheets sheets Initial sheets sheets Initial sheets sheetsInitial sheets sheets Ex- N/N 1.48 1.44 1.40 0.7 1.4 1.8 A A A A A A A AA am- H/H 1.45 1.40 1.35 0.7 1.5 1.7 A A A A A A A A B ple N/L 1.50 1.461.43 1.3 2.0 2.3 A A B A A A A A A 2-8 Ex- N/N 1.41 1.45 1.42 1.0 1.92.3 A A B A A A A A A am- H/H 1.45 1.43 1.38 0.9 1.8 2.1 A A A A A A A AB ple N/L 1.48 1.44 1.40 1.7 2.4 2.8 A B B A A B A A B 2-9 Ex- N/N 1.421.39 1.33 1.5 2.0 2.5 A A B A A A A A B am- H/H 1.37 1.33 1.25 1.2 2.12.3 A A A A A A A B C ple N/L 1.44 1.40 1.36 2.1 2.5 3.0 A B B A A A A AB 2-10 Com- N/N 1.37 1.17 1.04 1.7 2.5 3.0 A C D A C E B D F para- N/H1.30 1.03 0.92 1.6 2.4 2.9 A D E A C E C E G tive N/L 1.40 1.05 0.98 2.53.0 4.0 B E E B E F B E G Ex- am- ple 2-6 Com- N/N 1.42 1.22 1.14 1.52.2 2.9 B C D A B C A B C para- H/H 1.39 1.16 1.08 1.1 2.4 2.6 A B C A AB B C D tive N/L 1.35 1.11 1.05 2.2 2.7 3.3 C D E B C D B B C Ex- am-ple 2-7 Com- N/N 1.39 1.16 1.03 1.8 2.6 3.1 C D E B D F A C D para- H/H1.39 1.14 0.99 1.5 2.6 2.8 B C E A D B B D F tive N/L 1.26 1.04 0.94 2.72.9 3.6 D E E C E F B C F Ex- am- ple 2-8 Com- N/N 1.33 1.16 1.03 2.32.8 3.2 A B C A B D A C E para- H/H 1.19 1.04 0.89 1.9 2.7 2.9 A C D A BD B D F tive N/L 1.37 1.06 1.01 3.0 3.1 3.8 A D E A D E A C D Ex- am-ple 2-9

[0462] TABLE 2 6 Results of evaluating the durability on LBP730 (withrespect to Q/M, M/S and abrasion resistance) abrasion resistanceQ/M(mC/Kg) M/S(dg/m²) After Amount of 10,000 20,000 10,000 20,000Initial durability chipping Environment Initial sheets sheets Initialsheets sheets Ra(μm) Ra(μm) (μm) Example 2-8 N/N 16.7 17.0 17.1 1.811.78 1.78 1.62 1.58 1.5 H/H 15.8 15.7 15.4 1.75 1.73 1.70 1.62 1.35 1.9N/L 17.8 18.1 17.9 1.83 1.82 1.80 1.62 1.59 1.3 Example 2-9 N/N 16.915.7 15.2 1.83 1.76 1.71 1.65 1.63 1.1 H/H 16.1 14.8 13.9 1.77 1.71 1.641.65 1.61 1.5 N/L 17.8 17.1 16.1 1.90 1.75 1.62 1.65 1.63 1.0 ExampleN/N 15.1 14.5 13.9 2.20 2.08 1.99 2.30 2.08 2.4 2-10 H/H 14.0 13.4 12.92.04 1.93 1.81 2.30 1.93 2.8 N/L 15.9 15.4 14.8 2.28 2.10 1.95 2.30 2.122.1 Comparative N/N 13.6 12.3 8.7 1.71 1.39 1.01 1.51 0.84 6.3 Example2-6 H/H 11.4 9.4 6.9 1.60 1.06 0.79 1.51 0.73 7.4 N/L 14.3 11.0 7.9 1.751.09 0.84 1.51 0.88 5.9 Comparative N/N 15.6 14.0 11.2 1.75 1.41 1.221.57 1.52 1.3 Example 2-7 H/H 15.1 13.5 10.8 1.71 1.37 1.16 1.57 1.501.6 N/L 17.6 13.3 10.1 1.83 1.27 0.98 1.57 1.51 1.1 Comparative N/N 16.513.1 10.3 1.77 1.34 1.11 1.62 1.61 1.1 Example 2-8 H/H 15.9 12.5 9.91.73 1.31 1.04 1.62 1.59 1.4 N/L 18.0 11.8 9.2 1.84 1.19 0.92 1.62 1.610.9 Comparative N/H 12.8 11.6 10.8 2.01 1.51 1.15 2.02 1.05 6,0 Example2-9 H/H 10.2 9.0 8.1 1.89 1.18 0.87 2.02 0.97 6.8 N/L 13.6 12.1 11.02.09 1.24 0.91 2.02 1.11 5.6

EXAMPLE 2-11

[0463] 200 parts of resol-type phenol resin solution (containing 50%methanol);

[0464] 45 parts of graphitized particles (A-2-1);

[0465] 5 parts of conductive carbon black;

[0466] 12 parts of spherical particles a-2-8 (carbonized particlesobtained by baking phenol resin at 2,200° C.); and

[0467] 120 parts of methanol.

[0468] Glass beads of 1 mm in diameter were added as media particles ina mixture of the above materials and were then dispersed by a sand mill.Subsequently, the solid fraction in the resulting dispersion solutionwas diluted to 33% with methanol to obtain a coating solution.

[0469] Using the coating solution and a spray method, a resin coatingfilm was formed on an aluminum cylindrical tube having an outer diameterof 20 mmφ and an arithmetic mean roughness Ra of 0.4 μm prepared bygrinding. After that, the resin coating film was dried and hardened byheating in a direct drying furnace at 150° C. for 30 minutes to obtain adeveloper carrier B-2-11. The formulation and the physical properties ofthe resulting developer carrier B-2-11 are listed in Table 2-2.

[0470] The developer carrier B-2-11 was mounted on an image formingapparatus (Model: LBP950, manufactured by Canon Inc.) shown in FIG. 9.Here, the image forming apparatus had a developing device shown in FIG.7 and was equipped with a charging means for a contact roller andtransferring means for the contact roller. A durability evaluation testof the developer carrier was performed for printing 40,000 sheets whilesupplying one-component developer. The one-component developer used wasone containing the following components.

[0471] 100 parts of styrene-acrylic resin;

[0472] 100 parts of magnetite;

[0473] 1 parts of aluminum complex of di-tertiary butyl salicylic acid;and

[0474] 5 parts of low-molecular weight polypropylene.

[0475] The above materials were kneaded, pulverized, and classified by atypical dry toner method to obtain fine powders (toner particles) havingthe number-average particle size of 6.3 μm. Subsequently, 1.2 parts ofhydrophobic colloidal silica treated with a silane coupling agent wasexternally added to 100 parts of the fine powders to obtain magnetictoner. The resulting magnetic toner was provided as the one-componentdeveloper.

[0476] (Evaluation)

[0477] A durability test was performed with respect to the followingevaluation items for evaluating each of the developer carriers of theexamples and the comparative examples.

[0478] An evaluation test was performed by the same method as that ofExample 2-1 for evaluating image qualities with respect to imagedensity, fogging, sleeve ghost, blotch, uniformity of half-tone, and soon; the amount of charge on toner on the developer carrier (Q/M); thetransfer amount of toner (M/S); and the abrasion resistance of the resincoating layer. In addition, the stain resistance of the resin coatinglayer of the developer carrier was evaluated as follows. In each ofevaluating items, the durability evaluations were performed under thesurroundings of normal-temperature and normal-humidity (N/N, 20°C./60%), normal-temperature and low-humidity (N/L, 242C/10%), andhigh-temperature and high-humidity (H/H, 32° C./80%), respectively. Theresults are listed in Tables 1-7 and 1-8. As shown in the tables, goodresults were obtained for both the image qualities and durability.

[0479] (Stain Resistance of Resin Coating Layer)

[0480] The surface of developer carrier after the durability test wasobserved by magnifying by 200 times using a color laser 3D profilemicroscope manufactured by KEYENCE CORPORATION. The degree of tonerstain was evaluated on the basis of the following criteria.

[0481] A: Only a negligible amount of stain was observed.

[0482] B: A small amount of stain was observed.

[0483] C: Partial stain was observed.

[0484] D: Significant stain was observed.

EXAMPLE 2-12 TO EXAMPLE 2-14

[0485] Developer carriers B-2-12 to B-2-14 were obtained by the samemanufacturing method as that of Example 2-11 except that the graphitizedparticles A-2-2, A-2-3, and A-2-6 are respectively used as graphitizedparticles of the resin coating layer instead of A-2-1. The sameevaluation test as Example 2-11 was performed with the developer carrierB-2-12 to B-2-14. The formulation and the physical properties of theresin coating layer of the resulting developer carrier are listed inTable 2-2. The results of the evaluation tests are listed in Tables 2-7and 2-8.

Comparative Example 2-10 to Comparative Example 2-12

[0486] Developer carriers C-2-10 to C-2-12 were obtained by the samemanufacturing method as that of Example 2-11 except that the graphitizedparticles a-2-1, a-2-2, and a-2-3 are respectively used as graphitizedparticles of the resin coating layer instead of A-2-1. The sameevaluation test as Example 2-11 was performed with the developer carrierC-2-10 to C-2-12. The formulation and the physical properties of theresin coating layer of the resulting developer carrier are listed inTable 2-2. The results of the evaluation tests are listed in Tables 2-7and 2-8. TABLE 2 7 Results of evaluating the durability on LBP-950 (withrespect to image density, fogging, sleeve ghost, blotch, and uniformityof half-tone image) Uniformity of half- En- Image density Fogging Sleeveghost Blotch tone image viron- 20,000 40,000 20,000 40,000 20,000 40,00020,000 40,000 20,000 40,000 ment Initial sheets sheets Initial sheetssheets Initial sheets sheets Initial sheets sheets Initial sheets sheetsEx- N/N 1.49 1.45 1.42 0.8 1.0 1.2 A A A A A A A A A am- H/H 1.44 1.391.36 0.7 1.1 1.5 A A A A A A A A B ple N/L 1.50 1.47 1.45 1.1 1.4 1.7 AA A A A A A A A 2-11 Ex- N/N 1.46 1.44 1.40 1.0 1.5 2.2 A A A A A A A AB am- H/H 1.38 1.34 1.31 0.9 1.8 2.5 A A A A A A A B C ple N/L 1.47 1.431.37 1.4 2.3 2.8 A A B A A A A A B 2-12 Ex- N/N 1.47 1.40 1.35 1.2 1.72.5 A A A A A A A A B am- H/H 1.42 1.34 1.30 1.1 2.2 2.6 A A B A A A A BC ple N/L 1.48 1.38 1.33 1.6 2.4 2.9 A B B A A A A B B 2-13 Ex- N/N 1.471.45 1.42 0.9 1.2 1.9 A A A A A A A A A am- H/H 1.41 1.37 1.33 0.9 1.52.1 A A A A A A A A B ple N/L 1.48 1.45 1.41 1.2 1.9 2.4 A A B A A A A AB 2-14 Com- N/N 1.44 1.36 1.30 1.4 2.0 2.7 A B B A A A A B B para- H/H1.32 1.27 1.22 1.3 2.5 2.8 A A B A A A A C D tive N/L 1.45 1.32 1.28 1.72.6 3.2 A B C A A B A B C Ex- am- ple 2-10 Com- N/N 1.43 1.31 1.12 2.02.7 3.4 B C D A C C A B C para- H/H 1.33 1.22 1.08 1.7 2.5 3.2 A C D A BC B C D tive N/L 1.39 1.20 1.01 3.0 3.4 3.9 C D E B C D A B C Ex- am-ple 2-11 Com- N/N 1.45 1.37 1.18 1.7 2.4 3.0 A B C A A B A A B para- H/H1.37 1.29 1.15 1.5 2.3 2.8 A B C A A B A B C tive N/L 1.42 1.27 1.13 2.63.1 3.4 B C D A B C A B B Ex- am- ple 2-12

[0487] TABLE 2 8 Results off evaluating the durability on LBP-950 (withrespect to Q/M, M/S, abrasion resistance and stain resistance) abrasionresistance Q/M(mC/Kg) M/S(dg/m²) After Amount of 20,000 40,000 20,00040,000 Initial durability chipping Stain Environment Initial sheetssheets Initial sheets sheets Ra(μm) Ra(μm) (μm) resistance Example N/N17.2 16.0 14.7 2.12 2.06 1.94 2.03 1.92 1.6 A 2-11 H/H 16.0 14.8 13.32.01 1.90 1.82 2.03 1.88 1.9 A N/L 17.6 16.4 15.2 2.23 2.15 2.06 2.031.95 1.4 A Example N/N 16.0 14.6 13.3 2.09 1.98 1.86 1.98 1.83 2.0 A2-12 H/H 14.5 13.2 12.0 1.97 1.85 1.71 1.98 1.73 2.4 B N/L 16.4 14.913.6 2.18 2.07 1.94 1.98 1.87 1.7 B Example N/N 17.0 15.4 13.8 2.13 1.951.80 2.01 1.93 1.4 B 2-13 H/H 15.8 13.9 12.5 2.02 1.90 1.76 2.01 1.911.7 A N/L 17.8 14.8 13.5 2.18 1.97 1.82 2.01 1.92 1.2 B Example N/N 16.715.8 14.2 2.16 2.05 1.94 2.13 1.95 1.7 A 2-14 H/H 15.1 14.4 13.0 2.051.88 1.80 2.13 1.92 2.0 B N/L 17.2 16.0 14.7 2.26 2.14 2.02 2.13 2.011.5 A Comparative N/N 13.9 11.5 9.8 2.05 1.90 1.70 1.95 1.75 2.5 BExample H/H 12.5 10.1 8.1 1.92 1.75 1.53 1.95 1.65 3.1 D 2-10 N/L 15.011.0 9.2 2.12 1.89 1.63 1.95 1.82 2.3 C Comparative N/N 17.3 11.0 8.72.06 1.84 1.63 2.06 1.93 1.1 C Example H/H 15.8 9.7 7.5 1.95 1.68 1.442.06 1.80 1.3 E 2-11 N/L 17.5 10.4 7.8 2.20 1.76 1.51 2.06 1.89 0.9 DComparative N/L 17.3 11.6 9.3 2.07 1.87 1.68 2.04 1.96 1.2 B Example H/H15.9 10.8 8.2 1.94 1.73 1.49 2.04 1.85 1.5 D 2-12 N/L 17.7 11.4 8.4 2.161.82 1.58 2.04 1.92 1.1 C

EXAMPLE 2-15

[0488] 200 parts of MMA-DM (methyl methacrylate/dimethylaminoethylmethacrylate) copolymer (copolymerizing ratio=88/12, Mn=6,800,Mw=16,300, Mw/Mn=2.4, containing 50% ethyl acetate);

[0489] 28 parts of graphitized particles (A-2-1);

[0490] 3.5 parts of conductive carbon blacks; and

[0491] 9 parts of spherical particles a-2-2 (carbonized particlesobtained by baking phenol resin at 2,200° C.)

[0492] Glass beads of 1 mm in diameter were added as media particles in120 parts of ethyl acetate and were then dispersed by a sand mill.Subsequently, the solid fraction in the resulting dispersion solutionwas diluted to 25% with methanol to obtain a coating solution.

[0493] Using the coating solution and a spray method, a resin coatingfilm was formed on an aluminum cylindrical tube having an outer diameterof 16 mmφ and an arithmetic mean roughness Ra of 0.2 μm prepared bygrinding. After that, the resin coating film was dried and hardened byheating in a direct drying furnace at 150° C. for 30 minutes to obtain adeveloper carrier B-2-15. The formulation and the physical properties ofthe resulting developer carrier B-2-15 are listed in Table 2-2.

[0494] The developer carrier B-2-15 was evaluated as follows using animage forming apparatus obtained by reconstructing thecommercially-available LBP2030 (manufactured by Canon Inc.) as shown inFIG. 11. The reconstructed LBP-2030 apparatus shown in FIG. 11 includesa black developing device 84Bk, an yellow developing device 84Y, amagenta developing device 84M, and a cyan developing device 84C, inwhich each of these developing devices utilizes a non-magneticone-component developing process using a non-magnetic one-componentdeveloper shown in FIG. 8 and constitutes a rotary unit 84 provided as adeveloping system. A multiple toner image with the respective colortoners primarily transferred on an intermediate transfer drum 85 wassecondarily transferred to a recording medium P at once, followed byfixing the transferred multiple toner image on the recording medium P bythe application of heat.

[0495] Here, an elastic regulating member 11 (see FIG. 8) wasreconstructed by subjecting a polyamide polyether elastomer to theinjection molding at a Shore-D hardness of 40 degrees on a phosphorbronze thin plate.

[0496] Furthermore, a fixing device 83 shown in FIG. 11 was alsoreconstructed into the following configuration. A fixing roller 83 a ofthe fixing device 83 has a core axis made of aluminum coated with twokinds of layers. In a lower layer portion, a high-temperature vulcanizedsilicone rubber (HTV silicone rubber) was used as an elastic layer. Thethickness of the elastic layer was 1 mm and the hardness of the rubberwas 3° (JIS-A). In an upper layer potion, a mold releasing layer wasprepared as a thin film of 20 μm in thickness by spray coating atetrafluoroethylene/perfluoroxyl vinylether copolymer (PFA).

[0497] A pressure roller 83 b of the fixing device 83 is also designedjust as in the case of the fixing roller 83 a. That is, the core axisthereof is covered with a lower-layered silicone rubber elastic layerand an upper-layered fluoride resin mold releasing layer. The samematerials, thickness, and physical properties are applied.

[0498] The nip width of the fixing portion was 9.5 mm, the fixingpressure was 2.00×10⁵ Pa, and the surface temperature of the fixingroller at the time of being ready and waiting was set to 180° C. Amechanism for applying fixing oil was removed.

[0499] An intermediate transfer drum 85 was provided as an aluminumcylinder having an elastic surface layer made of a mixture of NBR andepichlorohydrin rubber with a thickness of 5 mm.

[0500] The following cyan toner was filled in the cyan developing device84 c of the reconstructed LBP-2030 apparatus, followed by conducting adurability test for 20,000 sheets under the following conditions.

[0501] Charging conditions: A direct voltage of −550 V and analternative voltage having a sine wave of 1,150 Hz and an amplitude of2.2 kVpp were superimposed with each other and were applied from a powersupply source (not shown) to the charge roller 82. The application ofthe voltage to the charge roller 82 allows the movements of chargestoward an insulating photosensitive drum 81 by means of electricdischarge to charge uniformly.

[0502] Developing conditions: A latent image was formed on the surfaceof the uniformly-charged photosensitive drum 81 by exposing to anirradiation of the laser light E. The strength of the laser beam wasadjusted such that the surface potential of the exposed portion was −180V.

[0503] A direct voltage of −330 V and an alternative voltage having asine wave of 2,200 Hz and an amplitude of 1.8 kVpp were superimposedwith each other and were applied on the cyan developing device 84C inFIG. 11 to generate an alternating electric field between the developingsleeve and the photosensitive drum 81 to blow out the toner for thedevelopment.

[0504] A primary transfer conditions: A direct voltage of +280 V wasapplied as a primary transfer bias voltage on the aluminum drum 85 a forthe primary transfer of a toner image formed by the developing device 84c on the photoconductor 81 to the intermediate transfer body 85.

[0505] A secondary transfer conditions: The toner image primarilytransferred on the intermediate transfer body 85 is further transferredto the recording medium P as a second transfer by the application of adirect voltage of +1,950 V as a secondary transfer bias to the transferunit 88.

[0506] The following cyan toner used in the above process was preparedas follows.

[0507] In 800 g of ion-exchanged water, 430 g of 0.1M-Na₃PO₄ aqueoussolution was added. The mixture was heated up to 63° C., followed bystirring at 16,000 rpm using the Clear Mix (manufactured by M TechniqueCo., Ltd.). After that, 73 g of 1.0M-CaCl₂ aqueous solution wasgradually added in the mixture, resulting in an aqueous mediumcontaining calcium phosphate salt.

[0508] On the other hand,

[0509] (Monomer) 162 g of styrene;

[0510] 38 g of n-butylacrylate;

[0511] (Coloring agent) 10 g of C.I. pigment blue 15:3;

[0512] (Charge-control agent) 2 g of aluminum complex of di-tertiarybutyl salicylic acid;

[0513] (Polar resin) 17 g of saturated polyester (an acid number of 10and a peak molecular weight of 8,500); and

[0514] (Mold-releasing agent) 25 g of ester wax (a melting point of 65°C.)

[0515] The mixture of the above formulation was heated up to 63° C. andwas then uniformly dissolved and dispersed using the Clear Mix, followedby the addition of 7 g of 2,2′-azobis (2,4-dimethyl valeronitrile) as apolymerization initiator. Consequently, a polymerizable monomercomposition was prepared.

[0516] The polymerizable monomer composition was added in the aboveaqueous medium. The mixture was stirred at 10,000 rpm by the Clear Mixfor 10 minutes at 63° C. under N₂ atmosphere to granulate thepolymerizable monomer composition. Subsequently, the mixture was stirredwith a paddle stirring blade to increase the temperature thereof up to75° C. to initiate the polymerization reaction in the mixture. Thereaction proceeded for 10 hours. After completing the polymerization,the remaining monomer was removed under reduced pressure at 80° C. Aftercooling, an appropriate amount of hydrochloric acid was added todissolve calcium phosphate salt, followed by filtrating, washing,drying, and classifying the product. Consequently, colored particles(colored toner particles) of 7.1 μm in particle size were obtained.

[0517] For 100 parts by mass of the resulting color particles, 1.2 partsby mass of hydrophobic silica (BET 290 m²/g) treated with 10 parts bymass of hexamethyldisilazane was externally added, resulting in cyantoner.

[0518] (Evaluation)

[0519] A durability test was performed with respect to the followingevaluation items for evaluating each of the developer carriers of theexamples and the comparative examples.

[0520] An evaluation test was performed for evaluating image qualitieswith respect to image density, fogging, uniformity of half-tone image,and so on; the amount of charge on toner on the developer carrier (Q/M);the transfer amount of toner (M/S); and the abrasion resistance of theresin coating layer; and stain resistance of the resin coating layer.Each of the evaluation test were conducted under the surroundings ofnormal-temperature and normal-humidity (N/N, 20° C./60%),normal-temperature and low-humidity (N/L, 24° C./10%), andhigh-temperature and high-humidity (H/H, 30° C./80%), respectively.

[0521] The results are listed in Tables 2-9 and 2-10. As shown in thetables, good results were obtained for both the image qualities anddurability.

[0522] (2-1) Image Density

[0523] Using a reflection densitometer RD918 (manufactured by Macbeth),the density of black solid image portion obtained by solid printing wasmeasured with respect to each of five different points on the image. Theaverage of the total measurement results was defined as the imagedensity.

[0524] (2-2) Fogging Density

[0525] The reflectivity (D1) of a white solid portion of the imageformed on a sheet of recording paper was measured. Furthermore, thereflectivity (D2) of a blank of another sheet of the same recordingpaper was measured. Then, the difference between D1 and D2 (i.e., thevalue of D1−D2) was obtained with respect to each of five differentpoints. The average of the total measurement results was defined as thefogging density. The reflectivity was measured using TC-6DS(manufactured by Tokyo Denshoku).

[0526] (2-3) Uniformity of Half-Tone Image (Generation of HazedDifference in Gradation, White Streak and White Belt)

[0527] The resulting image was visually observed with respect to hazeddifference in gradation, and linear or belt-shaped streak extending inthe direction of image formation generated particularly in a half-toneimage, followed by evaluating on the basis of the following criteria.

[0528] A: A uniform image.

[0529] B: A slight difference in gradation was observed when the imagewas carefully observed, but it was hardly recognized at a glance.

[0530] C: A hazed difference in gradation was observed, or linear- orbelt-like difference in gradation was observed from the distance, but itwas substantially no problem.

[0531] D: A hazed difference in gradation was observed, or linear- orbelt-like difference in gradation was observed, but practicallyallowable.

[0532] E: Shark skin-like haze was observed over the image, or streakcan be clearly recognized.

[0533] F: Poor image density and many streaks were observed in theimage.

[0534] (2-4) The Amount of Charge on Toner (Q/M) and the Transfer Amountof Toner (M/S)

[0535] Toner carried on the developing sleeve was absorbed and collectedinto a cylindrical metal tube and a cylindrical filter. At this time,the amount of charge per unit mass Q/M (mC/kg) and the mass of toner perunit area M/S(dg/m²) were calculated from the amount of electrostaticcharge Q accumulated in a capacitor through the cylindrical metal tube,the mass M of the collected toner, and the area S from which the tonerwas absorbed, to be defined as the amount of charge on toner (Q/M) andthe transfer amount of toner (M/S), respectively.

[0536] (2-5) Abrasion Resistance of Resin Coating Layer

[0537] The arithmetic mean roughness (Ra) of the developer carriersurface before and after the durability test and the amount of chippingin the film thickness of the resin coating layer were measured.

[0538] (2-6) Stain Resistance of Resin Coating Layer

[0539] The surface of developer carrier after the durability test wasobserved by magnifying by about 200 times using a color laser 3D profilemicroscope manufactured by KEYENCE CORPORATION. The degree of tonerstain was evaluated on the basis of the following criteria.

[0540] A: Only a negligible amount of stain was observed.

[0541] B: A small amount of stain was observed.

[0542] C: Partial stain was observed.

[0543] D: Significant stain was observed.

EXAMPLE 2-16 AND EXAMPLE 2-17

[0544] Developer carriers B-2-16 and B-2-17 were obtained by the samemanufacturing method as that of Example 2-15 except that the graphitizedparticles A-2-2 and A-2-3 are respectively used as graphitized particlesof the resin coating layer instead of A-2-1. The same evaluation test asExample 2-15 was performed with the developer carriers B-2-16 andB-2-17. The formulation and the physical properties of the resin coatinglayer of the resulting developer carrier are listed in Table 2-2. Theresults of the evaluation tests are listed in Tables 2-9 and 2-10.

Comparative Example 2-13 to Comparative Example 2-15

[0545] Developer carriers C-2-13 to C-2-15 were obtained by the samemanufacturing method as that of Example 2-15 except that the graphitizedparticles a-2-1, a-2-2, and a-2-3 are respectively used as graphitizedparticles of the resin coating layer instead of A-2-1. The sameevaluation test as Example 2-15 was performed with the developercarriers C-2-13 to C-2-15. The formulation and the physical propertiesof the resin coating layer of the resulting developer carrier are listedin Table 2-2. The results of the evaluation tests are listed in Tables2-9 and 2-10. TABLE 2 9 Results of evaluating the durability on LBP-2030(with respect to image density, fogging and uniformity of half- toneimage) uniformity of half-tone Image density Fogging image 10,000 20,00010,000 20,000 10,000 20,000 Environment Initial sheets sheets Initialsheets sheets Initial sheets sheets Example 2-15 N/N 1.50 1.47 1.43 0.81.0 1.4 A A A H/H 1.44 1.44 1.40 1.0 1.5 1.9 A A A N/L 1.45 1.42 1.391.4 1.8 2.3 A A B Example 2-16 N/N 1.48 1.44 1.40 1.1 1.3 1.7 A A A H/H1.44 1.39 1.35 1.4 1.9 2.3 A A B N/L 1.43 1.37 1.34 1.7 2.1 2.6 A A BExample 2-17 N/N 1.49 1.42 1.37 1.3 1.5 2.0 A A B H/H 1.45 1.37 1.33 1.52.1 2.5 A A B N/L 1.42 1.35 1.31 1.9 2.3 2.8 A B C Comparative N/N 1.451.38 1.29 1.1 2.3 3.0 A B C Example 2-13 H/H 1.39 1.32 1.18 1.6 2.5 3.2A B D N/L 1.43 1.33 1.20 2.3 2.8 3.8 A C D Comparative N/N 1.43 1.271.13 2.2 2.6 3.2 B C E Example 2-14 H/H 1.47 1.15 0.96 1.9 2.7 3.5 B D FN/L 1.35 1.09 0.91 3.0 3.7 4.4 C D E Comparative N/N 1.46 1.34 1.21 1.92.5 3.3 A B C Example 2-15 H/H 1.45 1.30 1.15 1.6 2.7 3.5 A C E N/L 1.401.26 1.10 2.4 3.2 4.0 B C E

[0546] TABLE 2 10 Results of evaluating the durability on LBP-2030 (withrespect to Q/M, M/S, abrasion resistance and stain resistance) abrasionresistance Q/M(mC/Kg) M/S(dg/m²) After Amount of 20,000 20,000 Initialdurability chipping Stain Environment Initial sheets Initial sheetsRa(μm) Ra(μm) (μm) resistance Example N/N 46.2 41.6 0.80 0.72 0.82 0.771.3 A 2-15 H/H 40.8 35.7 0.75 0.64 0.82 0.74 1.6 A N/L 49.1 42.5 0.860.74 0.82 0.78 1.1 A Example N/N 43.5 38.0 0.78 0.69 0.79 0.72 1.7 A2-16 H/H 36.4 31.1 0.72 0.60 0.79 0.68 2.1 B N/L 47.6 40.6 0.83 0.710.79 0.74 1.4 B Example N/N 45.7 38.5 0.81 0.69 0.83 0.79 1.1 B 2-17 H/H41.5 34.2 0.74 0.61 0.83 0.77 1.4 A N/L 47.3 36.7 0.87 0.65 0.83 0.761.0 B Comparative N/N 40.0 31.2 0.79 0.58 0.93 0.80 2.5 B Example H/H32.9 24.1 0.73 0.52 0.93 0.72 3.2 C 2-13 N/L 44.6 25.6 0.84 0.51 0.930.82 2.1 C Comparative N/N 46.6 24.6 0.77 0.52 0.87 0.86 1.0 D ExampleH/H 40.2 18.6 0.74 0.46 0.87 0.85 1.3 C 2-14 N/L 51.2 19.5 0.78 0.430.87 0.84 0.8 D Comparative N/N 46.7 29.0 0.80 0.57 0.88 0.85 1.2 BExample H/H 40.1 22.6 0.74 0.50 0.88 0.82 1.4 C 2-15 N/L 49.9 23.1 0.850.49 0.88 0.83 1.0 D

EXAMPLE 3-1 OF MANUFACTURING TONER

[0547] In a four-neck flask, 300 parts of xylene was placed. The insideof the flask was sufficiently replaced with nitrogen while stirring thecontents, followed by heating to reflux. Under the reflux, a mixture of68.8 parts by styrene, 22 parts by n-butyl acrylate, and 9.2 parts ofmonobutyl maleate, 1.8 parts of di-tert-butyl peroxide was graduallydropped in the flask for 4 hours, followed by being kept for 2 hours tocomplete the polymerization. Subsequently, the solvent was removed,resulting in polymer L1. The polymer L1 was subjected to GPC measurementand a peak molecular weight of 15,000 was obtained.

[0548] Next, 180 parts of deaerated water and 20 parts of 2% aqueoussolution of polyvinyl alcohol were placed in a four-neck flask, and thena mixture of 74.9 parts of styrene, 20 parts of n-butyl acrylate, 5.0parts of monobutyl maleate, and 0.2 parts of 2,2-bis(4,4-di-tert-butylperoxycycrohexyl) propane was added and stirred toobtain a suspension. Then, the inside of the flask was sufficientlyreplaced with nitrogen, followed by heating up to 90° C. to initiate thepolymerization. The temperature was kept for 24 hours to complete thepolymerization, resulting in polymer H1. After that, the polymer H1 isfiltrated and dried, and then subjected to GPC measurement to obtain apeak molecular weight of 800,000. Subsequently, the polymer L1 and thepolymer H1 were mixed in a xylene solution at a mass ratio of 70:30.Consequently, a binder resin 3-1 was obtained.

[0549] Previously, 100 parts of the above binder resin 1, 90 parts bymagnetic iron oxide (average particle size: 0.02 μm, magneticcharacteristic Hc at a magnetic field of 795.8 kA/m: 9.2 kA/m, ss: 82Am²/kg, sr: 11.5 Am²/kg), 3 parts of monoazo metal complex (negativecharge control agent), 3 parts of paraffin wax (a melting point of 75°C., a penetration (25° C.) of 6.5 mm, a number-average molecular weight(equivalent to polyethylene) of 390 measured by GPC), and 3 parts ofpolypropylene wax (a melting point of 143° C., a penetration (25° C.) of0.5 mm, a number average molecular weight (equivalent to polyethylene)of 1010 measured by GPC) were uniformly mixed. Then, the mixture wasdissolved and kneaded with a biaxial extruder heated at 130° C. Theresulting kneaded product was cooled and was then roughly pulverized bya hummer mill. Consequently, a powder raw material 3-A (rough pulverizedproduct) was obtained as a powder raw material for manufacturing toner.

[0550] The powder raw material 3-A was pulverized and classified by thedevice system shown in FIG. 16. As a mechanical pulverizer 301, TurboMill T-250 manufactured by Turbo Kogyo Co., Ltd. was used. The TurboMill was driven under the conditions in which the distance between arotor 314 and a stator 310 shown in FIG. 17 was 1.5 mm, and theperipheral speed of the rotor 314 was 130. m/s.

[0551] In this example, from a table-type first volumetric feeder 315,the powder raw material provided as the rough pulverized product wassupplied to the mechanical pulverizer 301 at a rate of 40 kg/h and wasthen pulverized. The powder raw material being pulverized in themechanical pulverizer 301 was collected into a cyclone 229 together withsuction air from an exhaust fan 224 and was then introduced into asecond volumetric feeder. Furthermore, at this time, the finelypulverized product obtained by pulverization in the mechanicalpulverizer 301 had a weight average diameter of 6.6 μm and showed asharp particle size distribution such that 40.3% by number of theparticles of 4.0 μm or less in particle size and 2.9% by volume ofparticles of 10.1 μm or more in particle size were included.

[0552] Next, the finely pulverized product obtained by the abovemechanical pulverizer 301 was subjected to an airflow classifier toremove rough powders and fine powders, resulting in a classified product(medium powders). In 100 parts of the classified product, 1.0 part ofhydrophobic silica fine powders (BET 120 m²/g) was externally added by aHenschel mixer (Model:FM-75, Mitsui Miike Kakoki, Co., Ltd.) to providetoner E-1 which is a one-component magnetic developer for evaluation.

EXAMPLE 3-1

[0553] A developing sleeve as a developer carrier was prepared by thefollowing method. At first, a coating solution for providing a resincoating layer on the surface of a developing sleeve was prepared at thefollowing blending ratio.

[0554] 400 parts by mass of resole phenol resin (50% of methanolsolution);

[0555] 40 parts by mass of graphitized particles A-3-1;

[0556] 40 parts by mass of graphite B-3-1;

[0557] 20 parts by mass of conductive carbon black;

[0558] 15 parts by mass of conductive spherical particle C-3-1; and

[0559] 280 parts by mass of isopropyl alcohol.

[0560] As graphitized particles, β-resin was extracted as graphitizedparticles by a solvent fractionation from coal tar pitch. Then, theβ-resin was hydrogenated and made heavier, followed by removing thesolvent soluble fraction by toluene to obtain a bulk mesophase pitch.The bulk mesophase pitch powders were pulverized, followed by oxidizingthe powder at about 300° C. in the air. Subsequently, under nitrogenatmosphere, the product was heated at 3,000° C. and was then classified.Consequently, graphitized particles A-3-1 having a number-averageparticle size of 3.84 μm were obtained. The physical properties of thegraphitized particles A-3-1 are listed in Tables 3-1a and 3-1b.Regarding the scaly or acicular-shaped graphite, the graphite B-3-1shown in Table 3-2 was used.

[0561] As spherical particles, using a Raikai device (Automatic mortar,manufactured by Ishikawa Kojo), 100 parts of phenol resin particleshaving a number-average particle size of 7.8 μm were coated with 14parts of coal bulk mesophase pitch powder having a number-averageparticle size of 2 μm or less. After heat stabilization at 280° C. inthe air, the product was baked at 2,000° C. under nitrogen atmospherefor graphitization and classified. Consequently, spherical conductivecarbon particles (spherical particles C-3-1) having a number-averageparticle size of 11.7 μm were obtained and used for the evaluation. Thetrue density of the spherical particles C-3-1 was 1.48 g/cm³, the volumeresistivity thereof was 8.5×10⁻² Ω·cm, and a ratio of majordiameter/minor diameter was 1.07.

[0562] The above material was dispersed by a sand mill using glassbeads. In the method of dispersion, the resole phenol resin (containing50% methanol) was diluted with part of isopropyl alcohol. Then, theconductive carbon black, the graphitized particles A-3-1, the graphiteB-3-1 were added in the mixture and dispersed by a sand mill using glassbeads of 1 mm in diameter were added as media particles in the mixture.Furthermore, the above conductive spherical particles C-3-1 were addedin the mixture, followed by proceeding sand mill dispersion to obtain acoating solution.

[0563] Using the above coating solution together with a spray method, aresin coating layer was formed on an aluminum cylindrical tube having anouter diameter of 20 mmφ. After that, the resin coating layer was driedand hardened by heating in a direct drying furnace at 150° C. for 30minutes to obtain a developer carrier D-1. The formulation and thephysical properties of the conductive coating layer of the resultingdeveloper carrier D-1 are listed in Tables 3-3a to 3-3d.

[0564] The evaluation of the developer carrier D-1 was performed using acommercially-available laser printer (Laser Jet HP9000, manufactured byHewlett-Packard Company). For the developer, the evaluation wasperformed using the toner E-1.

[0565] [Evaluation]

[0566] The durability test was performed with respect to the followingevaluation items to evaluate the developer carrier of each of theexamples and the comparative examples. In Tables 3-4a and 3-4b, theresults of the evaluations with respect to the durability of the imagedensity, durability to fogging, durability to ghost, abrasionresistance, and stain resistance at low temperature and low humidity areshown. In Tables 3-5a and 3-5b, the durability of image density,durability to fogging, durability of ghost, abrasion resistance, andstain resistance at normal temperature and normal humidity are shown. InTables 3-6a and 3-6b, furthermore, the evaluations of the durability ofimage density, durability of character sharpness, durability to ghost,abrasion resistance, and stain resistance at high temperature and highhumidity are shown.

[0567] The durability evaluation was performed under each of threesurroundings of low-temperature and low-humidity (L/L),normal-temperature and normal-humidity (N/N), and high-temperature andhigh-humidity (H/H). More specifically, the low-temperature andlow-humidity (L/L) was of 15° C./10% RH, the normal-temperature andnormal-humidity (N/N) was of 24° C./55% RH, and the high-temperature andhigh-humidity (H/H) was of 32.5° C./85% RH, respectively.

[0568] <Evaluation Method>

[0569] (3-1) Image Density

[0570] Using a reflection densitometer RD918 (manufactured by Macbeth),the density of black solid image portion obtained by solid printing wasmeasured with respect to each of five different points on the image. Theaverage of the total measurement results was defined as the imagedensity.

[0571] (3-2) Ghost

[0572] A development was performed on the tip portion of an image inwhich a white solid portion and a black solid portion were adjacent toeach other (at the first round of the sleeve rotation), and thedifference in gradation between white solid trace and black solid tracegenerated on the half-tone after the second round of the sleeve rotationwas mainly visually observed and compared so as to be referenced for themeasurement of image density. The evaluation results were represented onthe basis of the following criteria.

[0573] A: No difference in gradation was observed.

[0574] B: A slight difference in gradation was observed depending on theangle of sight.

[0575] C: A difference in gradation was observed, while the differencein image densities was 0.01 or less.

[0576] D: A difference in gradation was observed even though the edgewas not clear, but practically allowable.

[0577] E: A clear difference in gradation was observed to some extent,barely practically allowable.

[0578] F: A clear difference in gradation was observed and thedifference between image densities was observed, so that it could not bepractically used.

[0579] G: A large difference in gradation, and the difference betweenimage densities was 0.05 or more by the reflection densitometer.

[0580] (3-3) Fogging

[0581] The reflectivity of the white solid image was measured and alsothe reflectivity of unused transfer paper. The difference between themeasured values (the lowest reflectivity of the white solid image—thehighest reflectivity of unused transfer paper) was defined as thedensity of fogging. The degree of fogging was expressed by such a value.The standard of fogging with respect to the density of fogging wasdefined as follows. Here, the measurement of the reflectivity wasrandomly performed 10 times using TC-6DS (manufactured by Tokyo DenshokuCo.).

[0582] 1.5 or less: Substantially no change;

[0583] 1.5 to 2.5: Difference could be recognized if carefully observed;

[0584] 2.5 to 3.5: Fogging could be recognized by degrees;

[0585] 4.0: It was in the bottom of a practical use level and thefogging was confirmed at a glance; and

[0586] 5.0 or more: Considerably worse.

[0587] (3-4) Sharpness of Characters

[0588] Characters on the transfer paper imaged under the environment ofhigh-temperature and high-humidity (32.5° C., 85%) were magnified byabout 30 times and were then evaluated on the basis of the followingevaluation criteria.

[0589] A: Almost no scattering occurred and extremely sharp lines wereobserved;

[0590] B: Comparatively sharp lines with slight scattering;

[0591] C: A larger amount of scattering was observed and the lines werewashed out to some extent; and

[0592] D: Hardly attained to the above C level.

[0593] (3-5) Abrasion Resistance of Coating Layer

[0594] Before and after durability, the arithmetic mean roughness (Ra)of the surface of the developer carrier was measured.

[0595] (3-6) Stain Resistance of Resin Coating Layer

[0596] The surface of developer carrier after durability was observedusing a SEM. The degree of toner stain was evaluated on the basis of thefollowing criteria.

[0597] A: A negligible amount of stain was observed.

[0598] B: A small amount of stain was observed.

[0599] C: Partial stain was observed.

[0600] D: Significant stain was observed.

EXAMPLE 3-2

[0601] Developer carrier D-2 was prepared by the same method as that ofExample 3-1 except that the addition amount of the graphitized particlesA-3-1 used for the coating solution in Example 3-1 was changed from 40parts to 10 parts and the addition amount of the graphite B-3-1 waschanged from 40 parts to 70 parts. The physical properties of the resincoating layer of the developer carrier D-2 are listed in Tables 3-3a to3-3d. Using the developer carrier D-2, the durability evaluation testwas conducted just as in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-3

[0602] Developer carrier D-3 was prepared by the same method as that ofExample 3-1 except that the addition amount of the graphitized particlesA-3-1 used for the coating solution in Example 3-1 was changed from 40parts to 70 parts and the addition amount of the graphite B-3-1 waschanged from 40 parts to 10 parts. The physical properties of the resincoating layer of the developer carrier D-3 are listed in Tables 3-3a to3-3d. Using the developer carrier D-3, the durability evaluation testwas conducted just as in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-4

[0603] As graphitized particles, β-resin was extracted from coal tarpitch using a solvent fractionation. Then, the β-resin was made heavierwith hydrogenation, followed by removing the solvent soluble fractionwith toluene to obtain bulk mesophase pitch. The resulting bulkmesophase pitch powders were pulverized and were then oxidized at about300° C. in the air, followed by heating at 3,200° C. under nitrogenatmosphere. Subsequently, the graphitized particles A-3-2 having anumber-average particle size of 3.65 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-2 arelisted in Tables 3-1a and 3-1b.

[0604] Developer carrier D-4 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-2 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the resin coating layer ofthe developer carrier D-4 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-4, the durability evaluation test was conducted justas in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-5

[0605] As graphitized particles, β-resin was extracted from coal tarpitch using a solvent fractionation. Then, the β-resin was made heavierwith hydrogenation, followed by removing the solvent soluble fractionwith toluene to obtain bulk mesophase pitch. The resulting bulkmesophase pitch powders were pulverized and were then oxidized at about300° C. in the air, followed by heating at 2,300° C. under nitrogenatmosphere. Subsequently, the graphitized particles A-3-3 having anumber-average particle size of 3.55 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-3 arelisted in Tables 3-1a and 3-1b.

[0606] Developer carrier D-5 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-3 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the resin coating layer ofthe developer carrier D-5 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-5, the durability evaluation test was conducted justas in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-6

[0607] As graphitized particles, β-resin was extracted from coal tarpitch using a solvent fractionation. Then, the β-resin was made heavierwith hydrogenation, followed by removing the solvent soluble fractionwith toluene to obtain bulk mesophase pitch. The resulting bulkmesophase pitch powders were pulverized and were then oxidized at about300° C. in the air, followed by heating at 2,000° C. under nitrogenatmosphere. Subsequently, the graphitized particles A-3-4 having anumber-average particle size of 3.71 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-4 arelisted in Tables 3-1a and 3-1b.

[0608] Developer carrier D-6 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-4 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the resin coating layer ofthe developer carrier D-6 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-6, the durability evaluation test was conducted justas in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-7

[0609] As graphitized particles, β-resin was extracted from coal tarpitch using a solvent fractionation. Then, the β-resin was made heavierwith hydrogenation, followed by removing the solvent soluble fractionwith toluene to obtain bulk mesophase pitch. The resulting bulkmesophase pitch powders were pulverized and were then oxidized at about300° C. in the air, followed by heating at 3,000° C. under nitrogenatmosphere. Subsequently, the graphitized particles A-3-5 having anumber-average particle size of 9.62 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-5 arelisted in Tables 3-1a and 3-1b.

[0610] Developer carrier D-7 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-5 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1 and the addition amount of the conductive sphericalparticles C-3-1 was changed from 20 parts to 10 parts. The physicalproperties of the resin coating layer of the developer carrier D-7 arelisted in Tables 3-3a to 3-3d. Using the developer carrier D-7, thedurability evaluation test was conducted just as in Example 3-1 whilesupplying the toner E-1.

EXAMPLE 3-8

[0611] As graphitized particles, β-resin was extracted from coal tarpitch using a solvent fractionation. Then, the β-resin was made heavierwith hydrogenation, followed by removing the solvent soluble fractionwith toluene to obtain bulk mesophase pitch. The resulting bulkmesophase pitch powders were pulverized and were then oxidized at about300° C. in the air, followed by heating at 2,300° C. under nitrogenatmosphere. Subsequently, the graphitized particles A-3-6 having anumber-average particle size of 21.5 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-6 arelisted in Tables 3-1a and 3-1b.

[0612] Developer carrier D-8 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-6 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1 and the conductive spherical particles C-3-1 were notadded. The physical properties of the resin coating layer of thedeveloper carrier D-8 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-8, the durability evaluation test was conducted justas in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-9

[0613] As graphitized particles, β-resin was extracted from coal tarpitch using a solvent fractionation. Then, the β-resin was made heavierwith hydrogenation, followed by removing the solvent soluble fractionwith toluene to obtain bulk mesophase pitch. The resulting bulkmesophase pitch powders were pulverized and were then oxidized at about300° C. in the air, followed by heating at 2,300° C. under nitrogenatmosphere. Subsequently, the graphitized particles A-3-7 having anumber-average particle size of 1.72 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-7 arelisted in Tables 3-1a and 3-1b.

[0614] Developer carrier D-9 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-7 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the resin coating layer ofthe developer carrier D-9 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-9, the durability evaluation test was conducted justas in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-10

[0615] As graphitized particles, meso-carbon micro beads obtained byheating coal heavy oil were washed and dried, followed by beingmechanically dispersed with an atomizer mill. Then, the resultingpowders were subjected to primary heat treatment at 1,200° C. undernitrogen atmosphere for carbonization. Subsequently, the carbonizedproduct was subjected to a secondary dispersion using the atomizer milland heated at 2,800° C. under nitrogen atmosphere, followed byclassification. Consequently, the graphitized particles A-3-8 having anumber-average particle size of 4.81 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-8 arelisted in Tables 3-1a and 3-1b.

[0616] Developer carrier D-10 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-8 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the conductive coating layerof the developer carrier D-10 are listed in Tables 3-3a to 3-3d. Usingthe developer carrier D-10, the durability evaluation test was conductedjust as in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-11

[0617] As graphitized particles, meso-carbon micro beads obtained byheating coal heavy oil were washed and dried, followed by beingmechanically dispersed with an atomizer mill. Then, the resultingpowders were subjected to primary heat treatment at 1,200° C. undernitrogen atmosphere for carbonization. Subsequently, the carbonizedproduct was subjected to a secondary dispersion using the atomizer milland heated at 2,300° C. under nitrogen atmosphere, followed byclassification. Consequently, the graphitized particles A-3-9 having anumber-average particle size of 4.92 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-9 arelisted in Tables 3-1a and 3-1b.

[0618] Developer carrier D-11 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-9 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the conductive coating layerof the developer carrier D-11 are listed in Tables 3-3a to 3-3d. Usingthe developer carrier D-11, the durability evaluation test was conductedjust as in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-12

[0619] Developer carrier D-12 was prepared by the same method as that ofExample 3-1 except that the graphitized particles B-3-2 having anumber-average particle size of 4.12 μm were used instead of thegraphitized particles B-3-1 used for the coating solution in Example3-1. The physical properties of the graphitized particles B-3-1 arelisted in Table 2, and the physical properties of the resin coatinglayer of the developer carrier D-12 are listed in Tables 3-3a to 3-3d.Using the developer carrier D-12, the durability evaluation test wasconducted just as in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-13

[0620] Developer carrier D-13 was prepared by the same method as that ofExample 3-12 except that the graphitized particles A-3-2 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-12. The physical properties of the resin coating layer ofthe developer carrier D-13 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-13, the durability evaluation test was conductedjust as in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-14

[0621] Developer carrier D-14 was prepared by the same method as that ofExample 3-12 except that the graphitized particles A-3-4 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-12. The physical properties of the resin coating layer ofthe developer carrier D-14 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-14, the durability evaluation test was conductedjust as in Example 3-1 while supplying the toner E-1.

Comparative Example 3-1

[0622] As graphitized particles, β-resin was extracted from coal tarpitch using a solvent fractionation. Then, the β-resin was made heavierwith hydrogenation, followed by removing the solvent soluble fractionwith toluene to obtain bulk mesophase pitch. The resulting bulkmesophase pitch powders were pulverized and were then oxidized at about300° C. in the air, followed by heating at 1,500° C. under nitrogenatmosphere. Subsequently, the graphitized particles A-3-10 having anumber-average particle size of 3.91 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-10 arelisted in Tables 3-1a and 3-1b.

[0623] Developer carrier d-1 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-10 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the resin coating layer ofthe developer carrier d-1 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier d-1, the durability evaluation test was conducted justas in Example 3-1 while supplying the toner E-1.

Comparative Example 3-2

[0624] As graphitized particles, β-resin was extracted from coal tarpitch using a solvent fractionation. Then, the β-resin was made heavierwith hydrogenation, followed by removing the solvent soluble fractionwith toluene to obtain bulk mesophase pitch. The resulting bulkmesophase pitch powders were pulverized and were then oxidized at about300° C. in the air, followed by heating at 3,500° C. under nitrogenatmosphere. Subsequently, the graphitized particles A-3-11 having anumber-average particle size of 3.85 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-11 arelisted in Tables 3-1a and 3-1b.

[0625] Developer carrier d-2 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-11 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the resin coating layer ofthe developer carrier d-2 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier d-2, the durability evaluation test was conducted justas in Example 3-1 while supplying the toner E-1.

Comparative Example 3-3

[0626] As graphitized particles, meso-carbon micro beads obtained byheating coal heavy oil were washed and dried, followed by beingmechanically dispersed with an atomizer mill. Then, the resultingpowders were subjected to primary heat treatment at 1,200° C. undernitrogen atmosphere for carbonization. Subsequently, the carbonizedproduct was subjected to a secondary dispersion using the atomizer milland heated at 3,200° C. under nitrogen atmosphere, followed byclassification. Consequently, the graphitized particles A-3-12 having anumber-average particle size of 4.85 μm obtained by classification wereused. The physical properties of the graphitized particles A-3-12 arelisted in Tables 3-1a and 3-1b.

[0627] Developer carrier d-3 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-12 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the conductive coating layerof the developer carrier d-3 are listed in Tables 3-3a to 3-3d. Usingthe developer carrier d-3, the durability evaluation test was conductedjust as in Example 3-1 while supplying the toner E-1.

Comparative Example 3-4

[0628] Spherical phenol resin particles having a number-average particlesize of 6.40 μm were baked at 2,200° C. for graphitization, followed byclassification to obtain graphitized particles A-3-13 having a numberaverage particle size of 5.30 μm, which were used as graphitizedparticles. The physical properties of the graphitized particles A-3-13are listed in Tables 3-1a and 3-1b.

[0629] Developer carrier d-4 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-13 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the conductive coating layerof the developer carrier d-4 are listed in Tables 3-3a to 3-3d. Usingthe developer carrier d-4, the durability evaluation test was conductedjust as in Example 3-1 while supplying the toner E-1.

Comparative Example 3-5

[0630] Coke and tar pitch were baked at about 2,600° C. forgraphitization, followed by classification to obtain graphitizedparticles A-3-14 having a number-average particle size of 5.52 μm, whichwere used as graphitized particles. The physical properties of thegraphitized particles A-3-14 are listed in Tables 3-1a and 3-1b.

[0631] Developer carrier d-5 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-14 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-1. The physical properties of the conductive coating layerof the developer carrier d-5 are listed in Tables 3-3a to 3-3d. Usingthe developer carrier d-5, the durability evaluation test was conductedjust as in Example 3-1 while supplying the toner E-1.

Comparative Example 3-6

[0632] Developer carrier d-6 was prepared by the same method as that ofExample 3-1 except that the graphitized particles A-3-1 used for thecoating solution of Example 3-1 were not used while 80 parts by mass ofthe graphite B-3-1 was used. The physical properties of the conductivecoating layer of the developer carrier d-6 are listed in Tables 3-3a to3-3d. Using the developer carrier d-5, the durability evaluation testwas conducted just as in Example 3-1 while supplying the toner E-1.

EXAMPLE 3-2 OF MANUFACTURING TONER

[0633] The following toner was used.

[0634] 100 parts by mass of styrene acrylic resin;

[0635] 85 parts by mass of magnetite;

[0636] 2 parts by mass of positive charge control agent(triphenylmethane compound); and

[0637] 3 parts by mass of hydrocarbon wax.

[0638] The above materials were mixed by a Henschel mixer and themixture was then dissolved, kneaded, and dispersed using a biaxialextruder. The kneaded product was cooled and was then finely pulverizedby the pulverizer with a jet airflow. Furthermore, the mixture wassubjected to classification using the airflow classifier. Consequently,the classified product, which includes particles having weight-averageparticle size of 7.5 μm, a number ratio of a particle size of 4 μm orless of 20.0%, and a mass ratio of a particle size of 10.1 μm or more of12.0% in terms of distribution, was obtained. Next, hydrophobiccolloidal silica was externally added at an amount of 1.0 part by masswith respect to 100 parts by mass of the above classified product usingthe Henschel mixer to obtain toner E-2 as the one-component magneticdeveloper for the evaluation.

EXAMPLE 3-15

[0639] 400 parts by mass of resole phenol resin (50% of methanolsolution);

[0640] 40 parts by mass of graphitized particles A-3-1;

[0641] 40 parts by mass of graphite B-3-1;

[0642] 20 parts by mass of conductive carbon black;

[0643] 20 parts by mass of conductive spherical particle C-3-2; and

[0644] 200 parts by mass of isopropyl alcohol.

[0645] As spherical particles, using a Raikai device (Automatic mortar,manufactured by Ishikawa Kojo), 100 parts of phenol resin particleshaving a number-average particle size of 5.5 μm were coated with 14parts of coal bulk mesophase pitch powder having a number-averageparticle size of 1.5 μm or less. After heat stabilization at 280° C. inthe air, the product was baked at 2,000° C. under nitrogen atmospherefor graphitization and classified. Consequently, spherical conductivecarbon particles (spherical particles C-3-2) having a number-averageparticle size of 5.0 μm were obtained and used for the evaluation. Thetrue density of the spherical particles C-3-2 was 1.50 g/cm³, the volumeresistivity thereof was 7.5×10⁻² Ω·cm, and a ratio of majordiameter/minor diameter was 1.07.

[0646] The above material was dispersed by a sand mill using glassbeads. In the method of dispersion, the resole phenol resin (containing50% methanol) was diluted with part of isopropyl alcohol. Then, theconductive carbon black, the graphitized particles A-3-1, the graphiteB-3-1 were added in the mixture and dispersed by a sand mill using glassbeads of 1 mm in diameter were added as media particles in the mixture.Furthermore, the above conductive spherical particles C-3-2 were addedin the mixture, followed by proceeding sand mill dispersion to obtain acoating solution.

[0647] An aluminum cylindrical tube was ground such that the outerdiameter is 32 mmφ, the surface roughness Ra is 0.2 μm, and afluctuation is about 5 to 10 μm. In addition, a work having one sideequipped with a flange for the developing sleeve was prepared. The workwas made to stand on a rotary table, which was rotated while masking theend of the sleeve. The above coating solution was applied on the workusing a spray gun moving downward at a constant speed, followed bydrying and hardening it with a ventilating type drier at 150° C. for 30minutes to form a resin coatings layer, resulting in developer carrierD-15.

[0648] A magnet was attached to the developing sleeve and was fitted ina stainless steel flange. As an evaluation apparatus, a copying machineGP605 manufactured by Canon Inc. was reconstituted into a 70-sheetmachine and was then used. While supplying toner E-2, a continuousendurance up to 200,000 sheets was performed and evaluated. For theevaluation, the judgment was made based on the comprehensive imageevaluation and the durability of the coating layer. The evaluation wasconducted under each of the surroundings of normal-temperature andlow-humidity (N/L, 24° C./10%), normal-temperature and normal-humidity(N/N, 24° C./55%), and high-temperature and high-humidity (H/H,309C/80%), respectively. The results are listed in Tables 3-7a and 3-7b.As shown in the table, good results were obtained for both the imagequalities and durability.

[0649] [Evaluation]

[0650] (3-1) Image Density

[0651] In the copying machine, the density of copied image of blackcircle (5 mmφ) on a test chart having an image ratio of 5.5% was definedthrough the reflection density measurement with a reflectiondensitometer RD918 (manufactured by Macbeth) with respect to each offive different points on the image. The average of the total measurementresults was defined as the image density.

[0652] (3-2) Fogging

[0653] The reflectivity of the white solid image under the conditionssuitable for development was measured and also the reflectivity ofunused transfer paper. The difference between the measured values (thelowest reflectivity of the white solid image—the highest reflectivity ofunused transfer paper) was defined as the density of fogging. Thereflectivity was measured using TC-6DS (manufactured by Tokyo DenshokuCo.). When the measured value was confirmed by the visual observation,1.5 or less indicated that substantially no fogging is observedvisually; the value of about 2.0 to 3.0 indicated that fogging could berecognized if carefully observed; and the value of 4.0 or more indicatedthat fogging could be recognized at a glance.

[0654] (3-3) Blotch (Image Defect)

[0655] Various kinds of images including black solid, half-tone, andline images were formed. Image defects such as wave-like unevenness andblotch (dot-like unevenness), and defective toner coating on thedeveloping sleeve at the time of image formation were visually observedand the results of the observations were referenced to evaluate on thebasis of the following criteria.

[0656] A: Any blotch could not be observed on the image and the sleeve.

[0657] B: Blotch was slightly found on the half-tone image.

[0658] C: Blotch was observed to some extent on the half-tone image, butbarely practically allowable.

[0659] D: Blotch was also observed on the black solid image, which waspractically not allowable.

[0660] E: Blotch was observed remarkably on the black solid image.

[0661] (3-4) Sleeve Ghost

[0662] During the image endurance, after flowing white solid image, ablack solid thick character or ideographic image was placed on the whiteof an image chart corresponding to one round of the sleeve, and theremainder of the image chart was provided as half-tone. Then, the degreeof ghost of thick character or ideographic image to be generated on thehalf-tone image was evaluated.

[0663] A: No difference in gradation was observed.

[0664] B: A slight difference in gradation was observed

[0665] C: A small difference in gradation was observed but barelypractically allowable.

[0666] D: Difference in gradation was observed, which was not allowablein terms of practical use.

[0667] E: Significant difference in gradation was observed.

[0668] (3-5) Stain and Fusion of Toner on Sleeve (Stain Resistance andFusion Resistance)

[0669] After evaluating the image formation under each environment, thedeveloping sleeve was detached and was then subjected to afield-emission scanning microscope (FE-SEM) to observe the surface ofthe sleeve. The results were evaluated on the basis of the followingcriteria.

[0670] A. Stain and fusion were not observed at al.

[0671] B. Stain and fusion were slightly observed.

[0672] C. Stain and fusion were slightly observed, but barelypractically allowable.

[0673] D. Stain and fusion were observed, which were practicallyunallowable.

[0674] E. Significant stain and fusion were observed.

[0675] (3-6) Abrasion Resistance of Coating Layer

[0676] Arithmetic mean roughness (Ra) of the surface of the developercarrier was measured before and after the endurance.

EXAMPLE 3-16

[0677] Developer carrier D-16 was prepared by the same method as that ofExample 3-15 except that the graphitized particles A-3-2 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-15. The physical properties of the resin coating layer ofthe developer carrier D-16 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-16, the durability evaluation test was conductedjust as in Example 3-15 while supplying the toner E-2.

EXAMPLE 3-17

[0678] Developer carrier D-17 was prepared by the same method as that ofExample 3-15 except that the graphitized particles A-3-3 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-15. The physical properties of the resin coating layer ofthe developer carrier D-17 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-17, the durability evaluation test was conductedjust as in Example 3-15 while supplying the toner E-2.

EXAMPLE 3-18

[0679] Developer carrier D-18 was prepared by the same method as that ofExample 3-15 except that the graphitized particles A-3-4 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-15. The physical properties of the resin coating layer ofthe developer carrier D-18 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-18, the durability evaluation test was conductedjust as in Example 3-15 while supplying the toner E-2.

EXAMPLE 3-19

[0680] Developer carrier D-19 was prepared by the same method as that ofExample 3-15 except that the graphitized particles A-3-9 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-15. The physical properties of the resin coating layer ofthe developer carrier D-19 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier D-19, the durability evaluation test was conductedjust as in Example 3-15 while supplying the toner E-2.

Comparative Example 3-7

[0681] Developer carrier d-7 was prepared by the same method as that ofExample 3-15 except that the graphitized particles A-3-10 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-15. The physical properties of the resin coating layer ofthe developer carrier d-7 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier d-7, the durability evaluation test was conducted justas in Example 3-15 while supplying the toner E-2.

Comparative Example 3-8

[0682] Developer carrier d-8 was prepared by the same method as that ofExample 3-15 except that the graphitized particles A-3-11 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-15. The physical properties of the resin coating layer ofthe developer carrier d-8 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier d-8, the durability evaluation test was conducted justas in Example 3-15 while supplying the toner E-2.

Comparative Example 3-9

[0683] Developer carrier d-9 was prepared by the same method as that ofExample 3-15 except that the graphitized particles A-3-12 were usedinstead of the graphitized particles A-3-1 used for the coating solutionin Example 3-15. The physical properties of the resin coating layer ofthe developer carrier d-9 are listed in Tables 3-3a to 3-3d. Using thedeveloper carrier d-9, the durability evaluation test was conducted justas in Example 3-15 while supplying the toner E-2.

Comparative Example 3-10

[0684] Developer carrier d-10 was prepared by the same method as that ofExample 3-15 except that the graphitized particles A-3-1 used for thecoating solution of Example 3-15 were not used while 80 parts by mass ofthe graphite B-3-1 was used. The physical properties of the resincoating layer of the developer carrier d-10 are listed in Tables 3-3a to3-3d. Using the developer carrier d-10, the durability evaluation testwas conducted just as in Example 3-15 while supplying the toner E-2.TABLE 3 1a The physical properties of the graphitized particles Degreeof Particle graphitization Lattice spacing (Å) type p (002) d (002)A-3-1 Bulk mesophase 0.43 3.3658 pitch particles A-3-2 Bulk mesophase0.26 3.3598 pitch particles A-3-3 Bulk mesophase 0.70 3.3983 pitchparticles A-3-4 Bulk mesophase 0.94 3.4312 pitch particles A-3-5 Bulkmesophase 0.26 3.3590 pitch particles A-3-6 Bulk mesophase 0.46 3.3682pitch particles A-3-7 Bulk mesophase 0.51 3.3759 pitch particles A-3-8Meso-carbon 0.31 3.3656 micro beads A-3-9 Meso-carbon 0.53 3.3789 microbeads A-3-10 Bulk mesophase 1.08 3.4492 pitch particles A-3-11 Bulkmesophase 0.17 3.3566 pitch particles A-3-12 Meso-carbon 0.08 3.3502micro beads A-3-13 Phenol resin Incapable Incapable particlesmeasurement measurement A-3-14 Coke and tar 0.11 3.3550 pitch

[0685] TABLE 3 2a The physical properties of the graphitized particlesBaking Average degree Particle temperature of circularity Number-averagetype (° C.) (SF-1) particle size (μm) A-3-1 3000 0.68 3.84 A-3-2 32000.70 3.65 A-3-3 2300 0.72 3.55 A-3-4 2000 0.67 3.71 A-3-5 3000 0.71 9.62A-3-6 2300 0.71 21.5 A-3-7 3000 0.69 1.72 A-3-8 2800 0.75 4.81 A-3-92300 0.77 4.90 A-3-10 1500 0.69 3.91 A-3-11 3500 0.70 3.85 A-3-12 32000.73 4.85 A-3-13 2200 0.85 5.30 A-3-14 2600 0.60 5.52

[0686] TABLE 3 2 The physical properties of the graphites Average Degreeof Lattice degree of Particle Particle graphitization spacing (Å)circularity size type p (002) d (002) (SF-1) (μm) B-3-1 0.19 3.5652 0.598.60 B-3-2 0.31 3.3653 0.64 4.12

[0687] TABLE 3 3a Developer carriers Examples and Graphitized OtherSpherical Comparative Developer particles Graphite colorant Resinparticles Examples carrier g1 g2 c B R Example 3-1 D-1 A-3-1 B-3-1Carbon Phenol C-3-1 Example 3-2 D-2 A-3-1 B-3-1 Carbon Phenol C-3-1Example 3-3 D-3 A-3-1 B-3-1 Carbon Phenol C-3-1 Example 3-4 D-4 A-3-2B-3-1 Carbon Phenol C-3-1 Example 3-5 D-5 A-3-3 B-3-1 Carbon PhenolC-3-1 Example 3-6 D-6 A-3-4 B-3-1 Carbon Phenol C-3-1 Example 3-7 D-7A-3-5 B-3-1 Carbon Phenol C-3-1 Example 3-8 D-8 A-3-6 B-3-1 CarbonPhenol None Example 3-9 D-9 A-3-7 B-3-1 Carbon Phenol C-3-1 Example 3-10D-10 A-3-8 B-3-1 Carbon Phenol C-3-1 Example 3-11 D-11 A-3-9 B-3-1Carbon Phenol C-3-1 Example 3-12 D-12 A-3-1 B-3-2 Carbon Phenol C-3-1Example 3-13 D-13 A-3-2 B-3-2 Carbon Phenol C-3-1 Example 3-14 D-14A-3-4 B-3-2 Carbon Phenol C-3-1 Comparative d-1 A-3-10 B-3-1 CarbonPhenol C-3-1 Example 3-1 Comparative d-2 A-3-11 B-3-1 Carbon PhenolC-3-1 Example 3-2 Comparative d-3 A-3-12 B-3-1 Carbon Phenol C-3-1Example 3-3 Comparative d-4 A-3-13 B-3-1 Carbon Phenol C-3-1 Example 3-4Comparative d-5 A-3-14 B-3-1 Carbon Phenol C-3-1 Example 3-5 Comparatived-6 None B-3-1 Carbon Phenol C-3-1 Example 3-6

[0688] TABLE 3 3b Developer carriers Examples and Graphitized OtherSpherical Comparative Developer particles Graphite colorant Resinparticles Examples carrier g1 g2 c B R Example 3-15 D-15 A-3-1 B-3-1Carbon Phenol C-3-2 Example 3-16 D-16 A-3-2 B-3-1 Carbon Phenol C-3-2Example 3-17 D-17 A-3-3 B-3-1 Carbon Phenol C-3-2 Example 3-18 D-18A-3-4 B-3-1 Carbon Phenol C-3-2 Example 3-19 D-19 A-3-9 B-3-1 CarbonPhenol C-3-2 Comparative d-7 A-3-10 B-3-1 Carbon Phenol C-3-2 Example3-7 Comparative d-8 A-3-11 B-3-1 Carbon Phenol C-3-2 Example 3-8Comparative d-9 A-3-12 B-3-1 Carbon Phenol C-3-2 Example 3-9 Comparatived-10 None B-3-1 Carbon Phenol C-3-2 Example 3-10

[0689] TABLE 3 3c Developer carriers Examples and Volume resistivelyComparative c/g1/g2/B/R of resin coating Examples Mass ratio layer (Ω ·cm) Example 3-1 0.2/0.4/0.4/2/0.2 1.16 Example 3-2 0.2/0.1/0.7/2/0.20.83 Example 3-3 0.2/0.7/0.1/2/0.2 3.42 Example 3-4 0.2/0.4/0.4/2/0.21.04 Example 3-5 0.2/0.4/0.4/2/0.2 1.92 Example 3-6 0.2/0.4/0.4/2/0.22.56 Example 3-7 0.2/0.4/0.4/2/0.1 1.38 Example 3-8 0.2/0.4/0.4/2/0 1.91Example 3-9 0.2/0.1/0.7/2/0.2 0.75 Example 3-10 0.2/0.4/0.4/2/0.2 1.34Example 3-11 0.2/0.4/0.4/2/0.2 1.20 Example 3-12 0.2/0.4/0.4/2/0.2 1.41Example 3-13 0.2/0.4/0.4/2/0.2 0.95 Example 3-14 0.2/0.4/0.4/2/0.2 1.22Comparative 0.2/0.4/0.4/2/0.2 6.24 Example 3-1 Comparative0.2/0.4/0.4/2/0.2 0.69 Example 3-2 Comparative 0.2/0.4/0.4/2/0.2 0.75Example 3-3 Comparative 0.2/0.4/0.4/2/0.2 1.14 Example 3-4 Comparative0.2/0.4/0.4/2/0.2 1.36 Example 3-5 Comparative 0.2/0/0.8/2/0.2 0.49Example 3-6

[0690] TABLE 3 3d Developer carriers Examples and Volume resistivelyComparative c/g1/g2/B/R of resin coating Examples Mass ratio layer (Ω ·cm) Example 3-15 0.2/0.4/0.4/2.5/0.2 3.12 Example 3-160.2/0.4/0.4/2.5/0.2 2.48 Example 3-17 0.2/0.4/0.4/2.5/0.2 4.05 Example3-18 0.2/0.4/0.4/2.5/0.2 5.13 Example 3-19 0.2/0.4/0.4/2.5/0.2 2.97Comparative 0.2/0.4/0.4/2.5/0.2 8.47 Example 3-7 Comparative0.2/0.4/0.4/2.5/0.2 2.07 Example 3-8 Comparative 0.2/0.4/0.4/2.5/0.21.95 Example 3-9 Comparative 0.2/0/0.8/2.5/0.2 1.45 Example 3-10

[0691] TABLE 3 4a Results of the evaluations at low temperature and lowhumidity Evaluation items Durability number Image density foggingdurability to ghost of sheets Initial 3,000 50,000 Initial 3,000 50,000Initial 3,000 50,000 Example 3-1 1.45 1.43 1.44 1.4 1.7 1.8 B B AExample 3-2 1.43 1.42 1.40 1.6 1.7 1.9 B B A Example 3-3 1.42 1.41 1.421.5 1.6 2.0 B C B Example 3-4 1.44 1.43 1.41 1.3 1.6 1.7 B B A Example3-5 1.46 1.43 1.41 1.8 2.2 3.0 B C B Example 3-6 1.47 1.44 1.42 1.7 2.43.2 B D C Example 3-7 1.45 1.43 1.42 1.4 1.6 1.9 B B A Example 3-8 1.461.42 1.43 1.6 1.8 1.9 B B A Example 3-9 1.42 1.42 1.40 1.9 1.9 2.1 B B AExample 3-10 1.43 1.40 1.41 1.7 1.8 1.9 B B A Example 3-11 1.42 1.411.40 1.5 1.7 1.8 B B A Example 3-12 1.43 1.41 1.44 1.8 1.9 2.0 B B AExample 3-13 1.44 1.42 1.42 1.7 1.9 2.1 B B A Example 3-14 1.42 1.411.43 1.9 2.2 3.1 B D C Comparative 1.42 1.40 1.30 2.0 2.7 4.5 C F DExample 3-1 Comparative 1.44 1.41 1.36 1.8 2.1 2.6 B C B Example 3-2Comparative 1.43 1.10 1.38 1.7 2.0 2.4 B C B Example 3-3 Comparative1.41 1.40 1.33 2.1 2.6 3.8 C F D Example 3-4 Comparative 1.44 1.42 1.351.8 2.1 2.5 B C B Example 3-5 Comparative 1.42 1.41 1.39 1.6 2.0 2.2 B CA Example 3-6

[0692] TABLE 3 4b Results of the evaluations at low temperature and lowhumidity abrasion resistance Before After durability durability Ra stainresistance Evaluation items Ra (μm) (μm) After durability Example 3-11.38 1.21 A Example 3-2 1.42 1.12 A Example 3-3 1.35 1.26 B Example 3-41.36 1.18 A Example 3-5 1.33 1.20 B Example 3-6 1.37 1.23 C Example 3-71.30 1.15 A Example 3-8 1.45 1.29 A Example 3-9 1.32 1.10 A Example 3-101.36 1.20 A Example 3-11 1.33 1.20 A Example 3-12 1.37 1.23 A Example3-13 1.34 1.17 A Example 3-14 1.39 1.23 B Comparative 1.30 1.13 CExample 3-1 Comparative 1.32 1.06 A Example 3-2 Comparative 1.35 1.08 AExample 3-3 Comparative 1.33 1.09 B Example 3-4 Comparative 1.31 1.14 AExample 3-5 Comparative 1.33 1.13 A Example 3-6

[0693] TABLE 3 5a Results of the evaluations at normal temperature andnormal humidity Evaluation items Durability Image density durability toghost number of sheets Initial 3,000 50,000 Initial 3,000 50,000 Example3-1 1.46 1.45 1.44 A A A Example 3-2 1.44 1.44 1.41 A A A Example 3-31.43 1.44 1.42 A A B Example 3-4 1.44 1.43 1.41 A A A Example 3-5 1.451.45 1.43 A A B Example 3-6 1.47 1.44 1.41 A A B Example 3-7 1.46 1.451.43 A A A Example 3-8 1.46 1.43 1.42 A A A Example 3-9 1.44 1.44 1.41 AA A Example 3-10 1.43 1.42 1.41 A A A Example 3-11 1.45 1.43 1.42 A A AExample 3-12 1.44 1.44 1.42 A A A Example 3-13 1.44 1.45 1.40 A A AExample 3-14 1.43 1.42 1.39 A A C Comparative 1.44 1.40 1.38 B C DExample 3-1 Comparative 1.44 1.42 1.37 A A B Example 3-2 Comparative1.45 1.42 1.39 A A B Example 3-3 Comparative 1.42 1.41 1.37 A B CExample 3-4 Comparative 1.43 1.41 1.40 A B C Example 3-5 Comparative1.43 1.41 1.41 A A B Example 3-6

[0694] TABLE 3 5b Results of the evaluations at normal temperature andnormal humidity abrasion resistance Before After durability durabilityRa stain resistance Evaluation items Ra (μm) (μm) After durabilityExample 3-1 1.36 1.22 A Example 3-2 1.39 1.14 A Example 3-3 1.34 1.26 BExample 3-4 1.37 1.19 A Example 3-5 1.35 1.20 A Example 3-6 1.35 1.22 BExample 3-7 1.32 1.16 A Example 3-8 1.48 1.28 A Example 3-9 1.36 1.11 AExample 3-10 1.34 1.19 A Example 3-11 1.33 1.20 A Example 3-12 1.31 1.21A Example 3-13 1.33 1.16 A Example 3-14 1.35 1.22 B Comparative 1.321.15 B Example 3-1 Comparative 1.34 1.09 A Example 3-2 Comparative 1.331.10 A Example 3-3 Comparative 1.33 1.11 B Example 3-4 Comparative 1.361.13 A Example 3-5 Comparative 1.35 1.13 A Example 3-6

[0695] TABLE 3 6a Results of the evaluations at high temperature andhigh humidity Evaluation items Sharpness of Durability number Imagedensity Durability to ghostv characters of sheets Initial 3.000 50,000Initial 3,000 50,000 Initial 3,000 50,000 Example 3-1 1.44 1.45 1.42 A AA A A A Example 3-2 1.43 1.44 1.39 A B B A A B Example 3-3 1.43 1.411.42 A B C A A B Example 3-4 1.44 1.42 1.39 A A B A A B Example 3-5 1.441.42 1.38 A B C A A B Example 3-6 1.45 1.44 1.36 B B D A A B Example 3-71.44 1.42 1.41 A A A A A A Example 3-8 1.46 1.44 1.42 A A A A A BExample 3-9 1.42 1.40 1.40 A A B A A B Example 3-10 1.44 1.41 1.41 A A AA A A Example 3-11 1.43 1.44 1.42 A A A A A A Example 3-12 1.43 1.421.41 A A A A A A Example 3-13 1.44 1.41 1.39 A A B A A B Example 3-141.42 1.40 1.35 B B D A A B Comparative 1.41 1.38 1.33 C D F B B CExample 3-1 Comparative 1.42 1.35 1.26 A B C A B D Example 3-2Comparative 1.43 1.33 1.22 A B C A B D Example 3-3 Comparative 1.42 1.381.30 B C E A B C Example 3-4 Comparative 1.42 1.40 1.35 A B D A B CExample 3-5 Comparative 1.41 1.40 1.36 A B C A B C Example 3-6

[0696] TABLE 3 6b Results of the evaluations at high temperature andhigh humidity Abrasion resistance Before After durability durability RaStain resistance Evaluation items Ra (μm) (μm) After durability Example3-1 1.36 1.17 A Example 3-2 1.39 1.10 B Example 3-3 1.36 1.24 C Example3-4 1.37 1.12 A Example 3-5 1.34 1.19 B Example 3-6 1.35 1.21 C Example3-7 1.32 1.11 A Example 3-8 1.47 1.26 A Example 3-9 1.33 1.06 B Example3-10 1.35 1.19 A Example 3-11 1.31 1.20 A Example 3-12 1.36 1.19 AExample 3-13 1.33 1.13 B Example 3-14 1.35 1.09 B Comparative 1.32 1.18D Example 3-1 Comparative 1.30 1.01 B Example 3-2 Comparative 1.36 1.02B Example 3-3 Comparative 1.34 1.05 C Example 3-4 Comparative 1.33 1.12B Example 3-5 Comparative 1.35 1.04 A Example 3-6

[0697] TABLE 3 7a Results of evaluating the durability on GP605Evaluation items Durability Image density Fogging number of 50,000200,000 500,000 200,000 sheets Initial sheets sheets Initial sheetssheets Example N/N 1.42 1.43 1.43 1.4 1.3 1.2 3-15 H/H 1.42 1.41 1.421.0 1.1 1.0 N/L 1.39 1.39 1.37 0.8 0.8 0.8 Example N/N 1.42 1.40 1.381.6 1.5 1.8 3-16 H/H 1.40 1.38 1.36 1.2 1.3 1.3 N/L 1.36 1.34 1.33 0.80.9 1.1 Example N/N 1.43 1.41 1.41 1.5 1.5 1.9 3-17 H/H 1.42 1.40 1.401.1 1.2 1.2 N/L 1.40 1.39 1.36 0.9 0.9 1.1 Example N/N 1.42 1.39 1.381.8 1.8 2.2 3-18 H/H 1.41 1.39 1.37 1.3 1.2 1.4 N/L 1.36 1.35 1.32 1.11.0 1.2 Example N/N 1.44 1.43 1.43 1.4 1.3 1.3 3-19 H/H 1.40 1.41 1.411.1 1.0 1.1 N/L 1.39 1.38 1.38 0.9 0.8 0.8 Comparative N/N 1.38 1.301.18 1.9 2.1 2.9 Example 3-7 H/H 1.36 1.28 1.19 1.5 1.6 1.9 N/L 1.301.21 1.01 1.4 1.6 2.4 Comparative N/N 1.37 1.31 1.19 1.9 2.0 2.8 Example3-8 H/H 1.37 1.28 1.17 1.6 1.6 2.2 N/L 1.30 1.20 1.02 1.3 1.3 1.6Comparative N/N 1.38 1.30 1.18 2.2 2.3 3.4 Example 3-9 H/H 1.37 1.291.21 1.6 1.8 2.4 N/L 1.31 1.18 1.04 1.2 1.4 1.5 Comparative N/N 1.291.18 0.92 3.0 3.1 4.1 Example H/H 1.28 1.20 1.01 2.0 2.4 3.3 3-10 N/L1.24 1.15 0.80 1.5 1.6 2.6

[0698] TABLE 3 7b Results of evaluating the durability on GP605 Abrasionresistance Evaluation items Stain and fusion (Surface roughness)Durability number of resistance 200,000 sheets After durability Initialsheets Example N/N A 0.82 0.80 3-15 H/H A 0.85 0.82 N/L B 0.83 0.79Example N/N B 0.82 0.79 3-16 H/H B 0.81 0.78 N/L C 0.79 0.74 Example N/NA 0.79 0.71 3-17 H/H A 0.82 0.78 N/L B 0.77 0.72 Example N/N A 0.79 0.773-18 H/H A 0.83 0.79 N/L B 0.85 0.74 Example N/N A 0.92 0.89 3-19 H/H A0.86 0.83 N/L B 0.88 0.81 Comparative N/N C 0.85 0.81 Example 3-7 H/H C0.84 0.74 N/L D 0.82 0.77 Comparative N/N A 0.83 0.78 Example 3-8 H/H A0.87 0.77 N/L B 0.86 0.79 Comparative N/N A 0.91 0.83 Example 3-9 H/H A0.93 0.81 N/L B 0.87 0.68 Comparative N/N A 0.75 0.59 Example H/H A 0.810.56 3-10 N/L B 0.79 0.49

What is claimed is:
 1. A developer carrier that carries a developer forvisualizing an electrostatic latent image retained on an electrostaticlatent image-bearing member, wherein: the developer carrier comprises atleast a substrate and a resin coating layer formed on a surface of thesubstrate; the resin coating layer comprises at least graphitizedparticles (i) with a degree of graphitization p(002) of 0.20 to 0.95 andan indentation hardness HUT [68] of 15 to 60 or graphitized particles(ii) with a degree of graphitization p(002) of 0.20 to 0.95 and anaverage circularity SF-1, which is an average value of circularityobtained by the following expression (1), of 0.64 or more.Circularity=(4×A)/{(ML)²×π}  (1) [In the expression, ML represents themaximum length of Pythagorean theorem of a particle projected image, andA represents an area of the particle projected image.]
 2. A developercarrier according to claim 1, wherein the resin coating layer containsthe graphitized particles (i) with a degree of graphitization p(002) of0.20 to 0.95 and an indentation hardness HUT [68] of 15 to
 60. 3. Adeveloper carrier according to claim 2, wherein a coefficient offriction (μs) of the resin coating layer of 0.10 to 0.35.
 4. A developercarrier according to claim 2, wherein the graphitized particles (i) areobtained by graphitizing meso-carbon micro bead particles or bulkmesophase pitch particles.
 5. A developer carrier according to claim 2,wherein a number-average particle diameter of the graphitized particles(i) is 0.5 to 25 μm.
 6. A developer carryier according to claim 1,wherein the resin coating layer contains graphitized particles (ii) witha degree of graphitization p(002) of 0.20 to 0.95 and an averagecircularity SF-1, which is an average value of circularity obtained bythe expression (1), of 0.64 or more.
 7. A developer carrier according toclaim 6, wherein the graphitized particles (ii) are obtained bygraphitizing meso-carbon micro bead particles or bulk mesophase pitchparticles.
 8. A developer carrier according to claim 6, wherein anumber-average particle diameter of the graphitized particles (ii) is0.5 to 25 μm.
 9. A developer carryier according to claim 6, wherein theresin coating layer further contains conductive fine particles.
 10. Adeveloper carrier according to claim 6, wherein the resin coating layerfurther contains spherical particles which imparts unevenness to asurface of the resin coating layer and which has a number-averageparticle diameter of 1 to 30 μm.
 11. A developer carrier according toclaim 6, wherein the resin coating layer is a conductive coating layerwith a volume resistivity of 10⁻² to 10⁵ Ω·cm.
 12. A developer carrieraccording to claim 6, wherein an arithmetic mean roughness Ra of theresin coating layer is 0.3 to 3.5 μm.
 13. A developer carrier accordingto claim 6, wherein: the resin coating layer further comprises scaly oracicular graphite with a degree of graphitization P_(B)(⁰⁰²) of 0.35 orless; and the degree of graphitization P(002) of the graphitizedparticles (ii) and the degree of graphitization P_(B)(⁰⁰²) of the scalyor acicular graphite satisfy the following relationship: P_(B)(002)≦=P(002).
 14. A developer carrier according to claim 13,wherein the graphitized particles (ii) are obtained by graphitizingmeso-carbon micro bead particles or bulk mesophase pitch particles. 15.A developer carrier according claim 13, wherein a number-averageparticle diameter of the graphitized particles (ii) is 0.5 to 25 μm. 16.A developer carrier according to claim 13, wherein the resin coatinglayer further contains conductive fine particles.
 17. A developercarrier according to claim 13, wherein the resin coating layer furthercontains lubricating particles.
 18. A developer carrier according toclaim 13, wherein the resin coating layer further contains sphericalparticles which imparts unevenness to the resin coating layer.
 19. Adeveloper carrier according to claim 13, wherein the resin coating layerhas a volume resistivity of 10⁻² to 10⁵ Ω·cm.
 20. A developer carrieraccording to claim 13, wherein an arithmetic mean roughness Ra of theresin coating layer is 0.3 to 3.5 μm.
 21. A developing device whichcomprises: a developer container that receives a developer; and adeveloper carrier that carries the developer in a thin layer form, whichis received in the developer container; wherein: the device feeds thedeveloper carried on the developer carrier to a developing area thatfaces an electrostatic latent image-bearing member, and visualizes anelectrostatic latent image retained on the electrostatic latentimage-bearing member by developing the electrostatic latent image withthe developer which have been fed to the developing area, the developercarrier comprises at least a substrate and a resin coating layer formedon a surface of the substrate, and the resin coating layer comprises atleast graphitized particles (i) with a degree of graphitization p(002)of 0.20 to 0.95 and an indentation hardness HUT [68] of 15 to 60 orgraphitized particles (ii) with a degree of graphitization p(002) of0.20 to 0.95 and an average circularity SF-1, which is an average valueof circularity obtained by the following expression (1), of 0.64 ormore. Circularity=(4×A)/{(ML)²×π}  (1) [In the expression, ML representsthe maximum length of Pythagorean theorem of a particle projected image,and A represents an area of the particle projected image.]
 22. Adeveloping device according to claim 21, wherein the resin coating layercontains the graphitized particles (i) with a degree of graphitizationp(002) of 0.20 to 0.95 and an indentation hardness HUT [68] of 15 to 60.23. A developing device according to claim 22, wherein a coefficient offriction (μs) of the resin coating layer of 0.10 to 0.35.
 24. Adeveloping device according to claim 22, wherein the graphitizedparticles (i) are obtained by graphitizing meso-carbon micro beadparticles or bulk mesophase pitch particles.
 25. A developing deviceaccording claim 22, wherein a number-average particle diameter of thegraphitized particles (i) is 0.5 to 25 μm.
 26. A developing deviceaccording to claim 21, wherein the resin coating layer containsgraphitized particles (ii) with a degree of graphitization p(002) of0.20 to 0.95 and an average circularity SF-1, which is an average valueof circularity obtained by the expression (1), of 0.64 or more.
 27. Adeveloping device according to claim 26, wherein the graphitizedparticles (ii) are obtained by graphitizing meso-carbon micro beadparticles or bulk mesophase pitch particles.
 28. A developing deviceaccording claim 26, wherein a number-average particle diameter of thegraphitized particles (ii) is 0.5 to 25 μm.
 29. A developing deviceaccording to claim 26, wherein the resin coating layer further comprisesconductive fine particles.
 30. A developing device according to claim26, wherein the resin coating layer further comprises sphericalparticles which imparts unevenness to a surface of the resin coatinglayer and which has a number-average particle diameter of 1 to 30 μm.31. A developing device according to claim 26, wherein the resin coatinglayer is a conductive coating layer with a volume resistivity of 10⁻² to10⁵ Ω·cm.
 32. A developing device according to claim 26, wherein anarithmetic mean roughness Ra of the resin coating layer is 0.3 to 3.5μm.
 33. A developing device according to claim 26, wherein: the resincoating layer further comprises scaly or acicular graphite with a degreeof graphitization P_(B)(002) of 0.35 or less; and the degree ofgraphitization P(002) of the graphitized particles (ii) and the degreeof graphitization P_(B)(002) of the scaly or acicular graphite satisfythe following relationship: P _(B)(002)≦P(002).
 34. A developing deviceaccording to claim 33, wherein the graphitized particles (ii) areobtained by graphitizing meso-carbon micro bead particles or bulkmesophase pitch particles.
 35. A developing device according claim 33,wherein a number-average particle diameter of the graphitized particles(ii) is 0.5 to 25 μm.
 36. A developing device according to claim 33,wherein the resin coating layer further contains conductive fineparticles.
 37. A developing device according to claim 33, wherein theresin coating layer further contains lubricating particles.
 38. Adeveloping device according to claim 33, wherein the resin coating layerfurther contains spherical particles which imparts unevenness to theresin coating layer.
 39. A developing device according to claim 33,wherein the resin coating layer has a volume resistivity of 10⁻² to 10⁵Ω·cm.
 40. A developing device according to claim 33, wherein anarithmetic mean roughness Ra of the resin coating layer is 0.3 to 3.5μm.
 41. A process cartridge which integrally comprises at least (I) anelectrostatic latent image-bearing member for retaining an electrostaticlatent image and (II) developing means for forming the electrostaticlatent image into a developed image with a developer in a developingarea, the process cartridge is detachably attached to a main body of animage forming apparatus, wherein: the developing means comprises adeveloper container that receives the developer; and a developer carrierthat carries the developer in a thin layer form on a surface thereof,which is received in the developer container; the developer carrierfeeds the developer to the developing area; the developer carriercomprises at least a substrate and a resin coating layer formed on asurface of the substrate; and the resin coating layer contains at leastgraphitized particles (i) with a degree of graphitization p(002) of 0.20to 0.95 and an indentation hardness HUT [68] of 15 to 60 or graphitizedparticles (ii) with a degree of graphitization p(002) of 0.20 to 0.95and an average circularity SF-1, which is an average value ofcircularity obtained by the following expression (1), of 0.64 or more.Circularity=(4×A)/{(ML)²×π}  (1) [In the expression, ML represents themaximum length of Pythagorean theorem of a particle projected image, andA represents an area of the particle projected image.]